I just got my vox populi badge, which says in the description that I used my 40 votes this day. My vote counter now shows 32 votes for today, and two of them I casted after the badge - which means, I got it by voting for only 30 answers/questions (or even less).
I also used quite a number of flags, edit approvals/rejects and close votes today, maybe these are counted here, too?
This is similar to a previous bug report Undeserved Vox Populi badge, that got closed (as a duplicate to Daily vote limit hit before reaching actual counts?, which got the completed tag) - but obviously the bug is still here, since I just observed it.