Hehehe, that's clever. Took me a few minutes to figure it out. That little formula you do to pick a number ends up with the same symbol no matter what you choose. Try it 3 or 4 times without clicking the crystal ball, and you'll end up with the same each time. Then when the list refreshes, you'll see all the symbols are shuffled around so they no longer match up to the same numbers, which is why it always ends up guessing a different symbol.
Sorry, us geeks ruined all the fun yet again.