i think the opposite. for every .22 you go, it thinks you went .25. so it gives you .03 for every .25 you go. i'm only assuming that it works this way though
I ran .25 and it ws reported as .25. That means that had I gone a whole mile, it would have reported .88. Had I gone 10 miles it would have reported 8.8 miles.
So that definitely under-reporting the mileage... unless I'm not understanding you.