On my activity impact page, it says I have cast 45 votes:
However, when I click on the link, and go to my votes cast details, it says I have only cast 40 votes:
Why is there a difference between the number of votes?
Meta Stack Exchange is a question and answer site for meta-discussion of the Stack Exchange family of Q&A websites. It only takes a minute to sign up.Sign up to join this community
The number in the impact box of activity page includes your votes on the posts that were deleted since you voted. The "votes" tab doesn't include deleted posts (so it does mean that 5 posts you voted on were later deleted) - unless you reach 10,000 reputation and can see deleted posts; but it only applies to close/reopen, (un)deletion votes, not to upvotes or downvotes.
Also maybe the votes in your "votes" tab aren't filtered by "all" - it could be the reason of it displaying less votes than impact box.
(Actually "votes">"all" also includes close, reopen, (un)deletion votes, but I assume you didn't cast them - certainly not close and reopen votes, otherwise the impact box would show less votes)