Reputation score is denormalized, so it is expected for it to vary slightly from the "real" value over time. We periodically recalculate everyone's reputation to bring it in sync, roughly once per year.
Some ways reputation can be affected without being updated live:
- a user is deleted; this deletes all their votes
- a post is deleted
- a post is migrated to another site
You can always check
to see the live calculation of your reputation, and optionally recalculate it to reflect the current, most correct, value.