Q. In your Revelation study guide you say that there’s a symbolic meaning for the numbers in the book. 3 means God, 4 means creation, 7 means perfection, 10 means completeness, and so forth. Did John really write with all of this in mind?
(The Revelation study guide can be read online or downloaded for free from this link.)
I believe he definitely did. Throughout the book of Revelation, John is drawing on a stock of recognizable symbols from the First Testament. This stock includes some commonly-used numerical symbols that would have been meaningful to John’s readers.
For example, in the First Testament, 10 represents completeness in the human dimension, since people usually have ten figures and ten toes. That’s why God gave an 
epitome of the law in the Ten Commandments. The number is also used in this sense when Job says to his friends, “Ten times now you have reproached me.” This is not a literal count, because the friends have only spoken five times to that point in the book. But the number means “You’ve reproached me as many times as a human can bear.” Ten meaning what is complete or ultimate in human experience is also seen in Daniel’s vision of the four beasts. The last one, representing a supreme empire, has ten horns. The image and the number with its significance are echoed in John’s description of the dragon in Revelation.
To give another example, since there were twelve tribes of Israel, the number 12 represents the covenant community in the First Testament. In the New Testament, Jesus himself appealed to this symbol when he chose 12 apostles. Through this number he was declaring that a new kind of covenant community was coming into existence through his life and ministry. In Revelation the number 12 is used throughout the book to represent the community. See how many times it’s used in the depiction of the New Jerusalem, for example. (See the Daniel-Revelation study guide, p. 131.)
Twelve can also be used in multiples and in combination with other numbers. There are 24 elders in the heavenly throne vision to depict the continuity of the first and new covenant communities. The number 144,000, for its part, comes from 12 x 12 x 10 x 10 x 10, representing the fullness of the community of believers throughout time and space from the first and new covenants. (I have a separate post about this, “Who are the 144,000 in the book of Revelation?“)
Examples like these show us what an intentional part numbers play in the book of Revelation’s symbolism, echoing the First Testament background. As for some of the other numbers in the book, as I write in my Daniel-Revelation study guide:
• 3 represents God, who’s often described in three-part phrases (“who was, and is, and is to come”) and ascribed triple attributes (“holy, holy, holy”; “glory and honor and power.”)
• 4 is the number of creation. It’s represented in the heavenly throne vision by four living creatures, and it’s also described as having four parts: heaven, earth, under-earth, and sea. The song of every creature ascribes four attributes to the Lamb: praise, honor, glory and power. There are other uses of the number 4 to symbolize creation later in the book, for example, in the following vision, “four angels standing at the four corners of the earth holding back the four winds”.
• The number 7 (4+3) represents perfection and completeness. The Lamb has seven horns and seven eyes; these symbolize his absolute power and knowledge. The scroll has seven seals because it contains the definitive judgments of God. The seven churches at the beginning of the book are symbolized by seven lamp stands and seven stars. While these are actual churches, they’re also representative of the church as a whole; what’s written to them is also addressed to the wider community of Jesus’ followers. The throne vision depicts the “seven spirits of God.” As a translation note in the NIV explains, this is the “seven-fold” Spirit of God–the perfect (divine) Holy Spirit. The angels, in their song, ascribe seven attributes to the Lamb, acknowledging his divine perfections.
We see in all of these ways, as I write in my study guide, that “in addition to visual symbols drawn from earlier Scriptures, the book of Revelation also uses numerical symbols. Certain numbers in the book are like ‘logos’ that point to key characters and themes.”
For the symbolic meaning of the number 666, see this post.
Good Question 
What does it mean if for the past year I keep seeing the numbers or symbols in my life 3 0 4. They are the dominant numbers or symbols that keep coming up or waking up to or seeing when I look at the clock. Is there a special meaning to these numbers in my life ?
To give my honest opinion, I think this is probably just a coincidence. God speaks to us through a variety of means, including the Bible, our conscience, and the counsel of other people who have faith, but I don’t believe that God sends us coded messages in numeric form. So I’d encourage you not to worry about these numbers, and concentrate instead on the means we know God uses to speak to us. Thanks for your question.
The number 3 means very bad things in Revelation.
It is mentioned more than 15 times and only once is it used in good context.
ie, and the third part of trees was burnt up, and all green grass was burnt up.
and the third part of the sea became blood
And I saw three unclean spirits like frogs come out of the mouth of the dragon, and out of the mouth of the beast, and out of the mouth of the false prophet.
It’s actually the fraction “one third” that’s mentioned 15 times in Revelation, and as you say, it’s usually in the context of some kind of judgment. The number “three” itself is mentioned ten times, sometimes in connection with judgment but sometimes in connection with blessing (as in the case of the three gates leading into the New Jerusalem from every direction). More significantly, three-fold formulas are used to bless the triune God: “Holy, holy, holy”; “who was, and is, and is to come”; “The Spirit and the bride say, ‘Come!’ And let the one who hears say, ‘Come!’”
Thank you for this nice summary.