Check out the link I placed at the bottom. That's TER's explanation.
Couple of thought's. (or more)
To me performance score should be how well (or not) the provider did what she does. If she only gives BJ's then the 7, 8, 9, or 10 should rate how well she gave that BJ. We don't need the rate to tell what she offers. We can read her profile.
TER adds a service component to the performance. The lady can be given a rate no higher than 7 in performance unless she offers (note offers, she doesn't have to actually have done that extra service with the guy writing the review. She just has to offer it ie. it's on her TER profile as a Yes.) certain extra services. There are 5, Blow Job -without condom, Kissing - with tongue, Anal - Yes, and Really Bi - Yes, More than One Guy - Yes. Any 3 of these 5 will make her eligible for a score of 10.
What this amounts to is No matter how well she gives a BJ 7 is all she can get if she doesn't offer the extra's. This leaves the guy first checking to see if she qualifies for an 8, 9, or 10. Then he has to decide if her performance was worthy of an 8, 9, or 10.
The discussion of what sense this makes is for another time. If you do a search on this board and probably the General Discussion board you'll find many discussions of this topic.
-- Modified on 10/11/2013 8:18:04 PM
This is the thousandth time this has been brought up.
The answer is the system is far from perfect. You seem to like the car analogy, most of these gals are in the Mustang and Camaro zone, Not too many Ferraris or Maseratis. I can give a Mustang a 10 if I am happy, others say NO WAY. Some guys even (gasp) like Buicks. If it has enough options the car is able to get a 10.
The review is just a guideline to help you get an IDEA of what she is like. SOMEONE ELSE'S IDEA!
Have fun and stop overthinking the scoring quagmire.