Seems more akin to saying, since we see this runner on the track, he must have been running around the track for an undeterminable period of the past time. It's

Seems more akin to saying, since we see this runner on the track, he must have been running around the track for an undeterminable period of the past time. It's just as possible that the runner just started running when you saw him. All I wanted to know is if we observed the past path or inferred it. Seems a valid question to me, but whatever.