We pulled 4 RC's in this first lot, but the centering on 2 of them was pretty poor, even to the 'untrained' eye. The 2 that we sent in looked very well centred and most of the edges/corners looked pretty sharp. Besides that, it was just a 'wait and see' sort of thing!
If you read the grading guidelines, it is quite well explained as to how they decide on the grade for each of the 4 categories.
When you look at the grade scales, all I needed was for 1 of the 9 sub grades to be a 9.5 and it would have received an overall 9.5 grade Hence the idea of trying them again.