Ratings usually mean the following:
>8 I'd do her, even if it meant first taking it in the ass from her using a strap-on.
6-7 I'd do her if she didn't expect me to go down on her.
5 I'd do her if I was entoxicated.
4 I'd do her if no one ever found out.
3-2 I'd do her in total darkness.
1 Reserved for animals and mutants. Below threshold of normal horniness. Barely.
Dude 2: Um dude, that's your step mom.
Dude 1: Oh yeah...my bad. I mean I'd still hook up with her if I got the chance... she's definately an 8.5 any day of the week!
Dude 2: You are so fucked up dude. She's a 6.3 at best.