Not really that special, it just keeps changing the icon behind the number 18 for me =\ not really special...So far the best "mind reader" I have seen is the Darth Vader one. I think every number that you can get has the same icon...Look for yourself:
Number 9 - 18 - 36 - 45 - 63 - 64 - 70 - 72 - 81
All these numbers always have the same icon, and you can only get these numbers
Yeah, was about to say that also. I just kept looking at 9 and pressing the button. Only fooled me twice. Rarely will it give you the symbol for 0 (any 1 digit number is _:0+_=_) which it did twice for me so far, but I wasn't looking at #9's symbol at those times...