My computer counts what I believe is the time average, that is for the time it's awake (it sleeps after 5 minutes), it does distance/time, so that takes into account slowing down before a stop, waiting at a light etc. A lot of people here will post typical cruising speed as their average and it's a very different number and assumes they're going on a perfectly flat road with no headwind (and then they add 10-20% for good measure).