The code for updating Elo ratings is here: https://github.com/smogon/pokemon-showdown/blob/master/server/ladders-remote.ts#L150
In particular, the K variable represents the highest number of points it's possible to get from winning a match. At the introductory rating of 1000, K = 80, then it gradually scales down to 50 as your rating approaches 1100, and stays there until it drops to 40 above 1300. In order to get the maximum reward of 80 points, you need to have a 1000 rating, somehow get paired against a much higher-rated player (such as 2000, which the matchmaker will heavily discourage unless there are no other players actively looking for games in that format at the time), and pull out a victory.
