PSL looks at quantifying facial features, which in univariate terms are positive rather than negative. It ignores the fact that someone can have negative features, such as Ryan gosling or Jared Leto, yet be attractive, or someone can be super attractive, but be overlay positive on PSL, such as Jason momoa or randy Orton.
Basically PSL is only relevant if u want to be a supermodel, ignores things like mix of features, harmony, overall impact of mannerisms and charisma and body posture, frame, muscle etc .
As a VERY rough guide take someone decile score (btw that's not a decile score, only 5% of men score 8+, not 20% of men, but anyway, their SMV or looks / 10 score and subtract 2-3 to get their PSL