An 8 is the standardized highest grade given by coordinators and their graders for an official for any specific down (which could be judgment, rules application, mechanics, or any combination). A 6 is a good, typical grade for making a call or doing something we all should be able to make. A 7 is something a little more difficult. An eight means something really special, and those are pretty uncommon. Having said that, I did get one once. I don't remember why, and, even at the time, I didn't think it was all that special. But, we take them when we get them and don't look a gift horse in the mouth.