Please explain how this works?

[polokid]

On the symbol puzzle next time you do it. Notice that all factors of 9 have the same symbol next to it. Everytime you do it, the symbols change, but they are always the same symbol for factors of 9. (factors of 9 are 9, 18, 27, 36, 45, 54, 63, 72, 81, 90, 99.....)
[signature]