She is the same species as Sebastian, a Runner, and Sebastian is shown to have 4 fingers instead of 5 during his card game.

Some of the species name are fictional.

A Runner would be a Raptor irl.

I don't really know about the Earth Dragon and Water Dragon irl. (maybe the -ceratops group?)

Adine never said that she is a wyvern, she called herself a 'flyer', it's the player who said that her appearance is akin to a wyvern, which is a mythical creature in the human mythology.

I don't think there is canonical answer ever told (as in written in plain text). Four does seem to be most likely, and one of them should be opposing for them to use tools easier (or hold hards). It's even worse with their hindpaws, and it doesn't help that whoever drew them had problem with perspective or never drew paws before. Anna is worst because she can look like she has two, three or four front ones, and it is implied in one of endings that she should have enlarged raptor toeclaw. Best way imo is to just go with whatever you think looks/works best.