Nut: you should be able to set you computer to either stopwatch or ATM. Actual Time Moving! (no...I have no idea what it really means but that's how I think of it.) If your computer is set for stopwatch it'll avg your spd based on total road time which could lower your avg. If you set it to ATM, ONLY the time the front tire is moving is measured. Check you manual: it should tell you if and or how to change your computer to ATM.

and no.....my avg spd is only about 13 +/- mph although when I'm on long straight flats I seem to avg about 16-17. My avg yesterday for my century was 14.?? which I was very proud of.