1. Kbin doesn’t federate downvotes from Lemmy, and I believe it has a smaller user population than Lemmy (or at least one that generates fewer total downvotes). So you’d expect downvote counts to be wildly different.
2. On upvote counts, federation is just real flaky right now. I don’t have GitHub issue links handy, but there are several major issues detailing posts, comments, and votes Federating unreliably. You can pretty easily extrapolate that to expect vote counts to vary by 20%-60% from server to server depending on how many federation messages a particular server decided to drop on the floor on any given day.

Lemmy is pretty cool, but it’s a lot rough around the edges right now. It’s improving fast, but if you break out the magnifying glass, you’re gonna find problems.