Reading from the top, the half-moons have the values 32, 16, 8, 4, 2, 1. White is on, black is off.

I'm tempted to say it's easy, but it would be disingenuous. I spent my entire working life programming computers, so hexadecimal--actually binary, in this context--is second nature. Try this: look at your eight volumes (excluding the Lexicon). In particular, look at the last five, Emphyrio plus Tschai, and note how the volume number advances by one as you go.

If that causes your eyes to cross or your head to ache, the Signature Series volume number is on the copyright page.