Where the 64 Gates came from
They are the 64 hexagrams of the Chinese “Book of Changes,” laid over the circle of the zodiac. Each Gate gets exactly 5 degrees 37 minutes 30 seconds of sky — the circle is divided into 64 equal parts. A planet that fell into such a part at your birth “switches on” that Gate in the chart.
Inside each Gate there are six more lines — the very six lines of the hexagram. Hence 384 shades: the same Gate sounds different in two people if the lines are different.
A Gate on its own is a half
Two Gates connected between centers make a channel, and that switches both centers on permanently. One Gate out of two is an open half: the theme is there, but it switches on only next to a person who has the other half. Hence the familiar “with this person I’m somehow not myself.”
Don’t try to learn them all
Sixty-four is a lot, and a beginner who starts here usually drowns and gives up. The order is different: first Type and Authority, then centers, and only then the Gates — and not in a row, but your own. They’re labeled in the calculation, so you won’t have to search blindly.