Disclaimer: I have not looked at how Lemmy calculates those numbers.

I suspect this is a combination of multiple factors:

• The stats could be averages over the last several days/weeks.
• The stats could be estimates, not exact numbers.
• The stats probably only account for people who look at the community directly.
• People do not need to look at the community to upvote a post, people can upvote from the site-wide feed.