Can anyone let me know why an upvote on an answer would yield +4 reputation, rather than the usual +10?
This seems to have occurred for one of my answers.
I am not concerned about it, I was just wondering.
You have hit the daily reputation cap (200, that is).
You can earn a maximum of 200 reputation per day from any combination of the activities below. Bounty awards, accepted answers, and association bonuses are not subject to the daily reputation limit.
Now you can get these badges:
The other situation that can result is unusual score changes is when an content that you've downvoted on gets deleted, or a user who has downvoted your content gets removed. As far as I can tell, there is no way to suss out the details of these actions, they just get rolled up into other score changes.
As @Hank noted, this occurred upon reaching the daily cap. I must have had 4 points remaining when the last upvote occurred. Thank you.