How do you contest already verified records?

If you think there is something wrong with a verified run, contact the game moderators about this with evidence. You should also probably ask the runner first about the issue, most likely there is a good explanation for whatever seems wrong to you.

There are no game moderators. https://www.speedrun.com/knowledgebase/about

It literally says there are currently 15,403 people as game moderators. If you are asking about how to find the moderators of a certain game, go to the leaderboard of the game, and you will see a list of the game moderators on the bottom left side.