PR, I believe, is "personal record". If you click into them, then I suspect that it'll show you over which segment...
Ah yes, that makes sense too.
I can't quite figure out what personal records are (I think I have 6 of them). I mean, it sounds obvious doesn't it? But I'm darned if I can figure out how they're worked out. I'm sure it's in the FAQ somewhere but who reads those?