I did think about this last night: about a year ago (maybe even longer at this point), when there was the SSR7 online race glitch that allowed people to finish 200 laps in about 10 minutes, I wonder if, for PD's purposes, that was counting the actual distance travelled by the GT-R (probably only a handful of miles' worth of donuts), or the intended race distance (roughly 2800 miles). There were people spending hours doing those races, buying up some of the 20 million dollar cars, and rinsing and repeating.
If PD is getting their numbers just based on an event's typical completed distance (no matter how the racers actually may have completed it, like the glitch), that could definitely have an inflating effect on the numbers.
On the other hand... does it count the endless amount of laps that took place in the near-daily "Open Track Day" rooms I had at the 'Ring back in late 2010 and early 2011, since those weren't technically races?