I realize there’s only a handful of symbols the mystic ball on this site can pick, but how does it know which one?

When you add the two digits of a two-digit number together and subtract the result from the original answer, you will always get a multiple of 9. All the symbols beside multiples of nine on that page are the same.

If you do the math the only values you can get are multiples of 9. if you look 0,9,18 etc are all the same symbol.

Ah, and so when you click to “try it again” all the multiples of 9 have a different symbol, so it appears to be random.

I think I’m going to save this site in my miiiiiiind and do some thought control experiments on my nieces and nephews!!!

(Insert evil laugh.)