Weird wizard thing...

[RedStratocas]

This is really simple. Whatever number you use, the result will be a multiple of nine, and all multiples of 9 are given the same symbol.

Exactly. Every number you choose can be one of only 10 possible numbers. All 10 numbers are the same symbol.

[Billay]

Exactly. Every number you choose can be one of only 10 possible numbers. All 10 numbers are the same symbol.

i dont get it,.

[Herman]

This is really simple. Whatever number you use, the result will be a multiple of nine, and all multiples of 9 are given the same symbol.

Ooh. So it's a math trick. I get it now.