Can someone explain to me how this gag works?

[Tied2thetracks]

http://www.milaadesign.com/wizardy.html

teh answer is always 9. damnit.

[livingdead7]

It got it right all ten times. I have no clue how it works...

[DeadJonas190]

It works because there are only a few possible answers. All of those answers have the same symbol, therefore it is always right. The trick is that it changes up the symbols everytime so it never seems to be the same

[livingdead7]

beat me to it...lol