Are you riding a bike or running a metrology lab? Since GPS and your computer measure distance using different methods they will never agree exactly. Rough or uneven road surfaces will make the wheel travel a farther distance than what GPS measures (to great precision I might add). Both are correct within their own frame of reference. Just take cnybikeman's advice and adjust your circumference setting and ride your bike. You are already at about 5% accuracy; make an adjustment once and call it good. If you keep comparing them and readjusting you will spend all of your time obsessing over the "correct" value instead of enjoying your ride.