I’m under the impression the reputation points are either the combined number of upvotes or that minus downvotes

IIRC from kbin – and assuming mbin didn’t change things – boosts counted for two points while upvotes (favorites) are one point and downvotes (reduces) are one point. Boosts are basically retweets, IIRC, and wouldn’t be coming from lemmy users – just from Mastodon, mbin, and other tools that support it.

Edit: To clarify, I mean downvotes reduce by one point.