A perfect nine?

I went out for a run today with a couple of guys from a lab upstairs. One of the guys is a pretty exceptional runner and runs ultras and the like (for those unfamiliar ultra-marathons are usually 50 plus miles). We went out for 80 minutes on a route that I figured was about 9 miles, but for some reason he thought it was 10. I checked tonight and it was closer to 9 miles. Regardless it was a great run and longer than I have been able to do in a long time. I might add that it was so warm out there today that I actually ran the second half of the run without my shirt. Fortunately most of the run was on a trail so no accidents were caused by the sun reflecting off my pasty white chest.