RidewithGPS only sees the raw data and performs it own calculation of average speed (for example). Depending on the lower speed limit you've set on your 500 it would be easy to accumulate a tenth of a mile or so additional in the RWG calculation.RWG may have a threshold setting as well, but I've not used it. Still, 32 miles versus 33 miles is a very big difference. Were you looking at difference to the nearest tenth of a mile?