Foxholer
Blackballed
My guess is that the NPR is the point beyond where the very existence of the track has changed the nature of the 'rest of the course' compared with how it would probably have been had the track not been there.
Well to continue in the slightly pedantic mode (not actually unreasonable here imo), it's purely about relief from the interference. Normally, the rough at the edge of the track is different (not cut as low) as that nearby. That 3-4 inches, or even more would be different if the trcak wasn't there, but it's not part of the track.
So purely 'edge of the track and a bit for the where a stroke wouldn't be interfered with by the track. Then drop within 1 club length.....