Its not like that. A girl that you classify as a 10, another guy may classify as a 5, so the whole rating idea is subject to personal opinion. Also, say the girl you are looking at, you think is a 10, she's not gonna go after you thinking "hes a 7, but ill give him a try/" To her, you will be a 9 or 10. To her you will be attractive.
We are not all classified universally as a number, 1-10 as we are a hair color or a gender.