I went to an information session this past June, and Mrs. Mailey suggested that it includes: 1) how competitive admission was for your undergraduate school (e.g., Cornell, Harvard, Yale, ... would put you at the top) and 2) quality of program (e.g., graduate degrees, honors, etc. so that someone with a PhD or MS would be above someone with a BS). This is just my understanding though, so it might be wrong! I certainly have NO clue about the mystery that is veterinary school admission
Someone posted on another thread that admissions offices choose applications to read by sticking them to the wall, throwing darts at them, and seeing which ones get hit. Sometimes I think that there are so many amazing candidates that the decision process is something similar lol.