They don't really mean anything when it's an estimation made by yourself. I keep seeing users rating themselves and I hardly see how it's relevant and most of the time it comes across as outright praising yourself (I'm an 8 / I used to be a 9 but I'm a 7 now... sad face).
I've been told I'm really pretty and beautiful too. And every woman I know gets told the same... Maybe you truly are a 9 but I probably won't believe it if it's self reported (and this is not because I don't believe a 9 exists, they do, it's more about the nature of the self-report). It also just makes me wonder what kind of perception people have of a 6, if 6 is still technically above average. Sometimes I think people assume it's like grading, and 6 has to be the lowest, fail score. Even if a guy has told you you're a 10, don't rule out the possibility that it's flattery to get in ya pants.
I think it's relevant info when your point is you're low on the spectrum and struggling with that, but besides that I assume you're average, and the average non-overweight girl is probably already on the pretty side. When I read someone posting they're 8 or 9 it's like reading "I'm an alpha", it's meaningless blabber.