Ratings are just an ordered list, with most of the scale used for describing things I like. >40% are for favourites, <9% are for dislikes after truncating.
These are arbitrary thresholds, the purpose of which are to facilitate the best tool out of the space.
Unrated were seen before account creation that I've remembered.
Above is copypasted from my ptp profile.
The percent scale is roughly mapped onto mal's 1-10. 1's are for any form of dislike, mild to extreme condensed into a single unit.
Any score of 2+ means I liked it, which is exceptional.