Is it 28 or 21?

Nub's advertises 28 km of groomed cross country ski trails. I skied them all yesterday, and the GPS unit puts the number of kilometers at a hair under 21. Over the years I've come to trust the GPS. I'll have to mention that to JB (the general manager of the resort) next time he's in for a sandwich. Anyway, I was shooting for a good solid two hour ski, and that's what I got. 21 km in 2:06 with 2,623 ft. of climbing, and an average heart rate of 148. I'm telemarking tonight at Nub's for the first time in a long time. Looking forward to riding the chairlift for a change of pace. Over and out.