It's quite easy , as there are only a few possible numbers that will come out.

if you pick 0 to 9 the answer is 0
10 to 19 = 9
20 to 29 = 18
30 to 39 = 27
etc

And guess what... those have all the same symbol

Spoil sport.

We noticed the answer just after I posted.

yeah did this before and it had me tricked until you realise they have the same symbol, but each time you do it the symbols change so you don't realise those numbers have the same symbol.