How does “Reputation” work?
For this answer, i have got +8 Rep.
As per my understanding,
REP = +10 per upvote, -2 per downvote.
Why I have got +8?
You can only net 200 reputation per day from includes upvotes, downvotes, suggested edits, etc. So if you for some reason get downvoted 50 times, and upvoted 50 times, you will receive (-100 + 500) = maximum = 200 reputation for the day.
(you can get more from accepted answers/bounties, which are counted differently, which is why you had +215 for the day)
See here for a much more detailed explanation of reputation.