Spanky, the rubric is right there at the top of the page, and answers what an 8.5, 9, and 9.5 would be.
I think Chris meant that the 8 is not what you are used to seeing on other sites; sites that typically only use the top five or six numbers of there scale.
In other words, this isn't school. A 7 (or 70%) isn't average. 5 is average, making an 8 a pretty good score. Check all of the links at the top of the page...your questions have all been answered.