in that, the higher the magnitude, the more enjoyable the movie is, but the more positive the movie, the better the movie is from a film standpoint.

For example, a well made movie that is also very enjoyable would be a 10, a horribly made movie but is very enjoyable would be a -10, and a bad movie that isnt fun at all would be a 0. I think balances the "critic" score and the "audience" score with RT.

I use my example of Prince of Persia. Its got bad rotten tomato score (36%), primarily due to it having poor storytelling, some cringe dialogue, and some cheap effects. however, I enjoy the PoP video game series, the movie captured the general spirit of the game, had a lot of fun effects and good music.
I'd rate it a -6. its a fun movie, but isnt a good movie.

I find this way to be the easiest to score movies like Hot Rod, Napolean Dynamite, Nacho Libre etc. Those arent 'good' movies, but they are very fun to watch.