So i've been messing around in some 18 man tourney's on stars, and i've noticed that the holdemresources ICM calculator can give very different results to the one i've just got with SNGwizard. Illustration:

HoldemResources.net: ICM Nash Calculator
(CO pushing 100% of their range)

now with exactly the same blinds, stacks, structure and everything, SNGwizard recommends shoving only 7.1%. This is a pretty massive difference, i'm wondering if it has to do with future game simulation (as UTG is very short), or am i just doing something wrong?

Any help appreciated.