Currently certain character attributes like "run speed" have a rank property that are hard-coded values taken from kuroganehammer.
See Link: https://github.com/ConnorBryan/smashcombos/blob/master/src/characters/bowser-jr.json#L9
Ideally, this can be expanded to calculate rank based on character values in comparison to all other N number of characters, allowing more flexibility as DLC characters are introduced.