This got me for a while too. Then my boyfriend told me to just randomly choose a number each time and sure enough the rodent began to get it wrong. It was then that I realised that there must only be certain numbers between 1 and 100 that you can feasibly end up with at the end of the specified formula and that they were obviously rotating the same symbols each time for all of them. Don't ask me what those figures are, though - I'm not a mathematician!
Thanks for that
Ingrid
(BTW I genuinely thought for a moment that that furry cartoon face just might be telepathic - don't tell anyone though!)