I found that John records only seven of Jesus' miracles. Since Revelation is full of sevens, and Revelation's chiasm has seven sections, it makes sense that John structured his gospel around the seven miracles of Jesus that he records.
Six of the seven miracles are recorded exclusively by John. The other three gospel writers don't mention them. But the central miracle in John's gospel, the feeding of the five thousand, is the only miracle recorded by all four gospel writers.
John tells us two reasons for his gospel in John 20:30, 31.
Here's a brief look at these seven miracles, and their chiastic relationships: