After emailing him a lot, from what I could gather, 1-3 (or 1-5 for H) represents different categories or big differences, the +'s represent orders of refinement. So 3 in grit means its fine, like a finisher, then each plus means harder. (rough, middle fine for grit) I could be very wrong but thats what it seems he means by it. Occasionally you'll see a - too, but usually its +'s.