Today, an answer I wrote to the question 'Why did Joseph Goebbels allow an all-Jewish Orchestra to exist and perform in Berlin from 1938 to 1941?' on History SE received an upvote. My reputation page credits this, as expected, as +10:
This also appears on the Recent Achievements (cup icon), but before I clicked on that icon the green notification said +2, not +10 (unfortunately, I can't screen shot that for proof as it disappeared when I clicked on it). Also, only 2 has been added to my reputation (this can presumably be checked by the powers that be). OK, this is no big deal and I figure this is just a minor glitch as there seems to be no other explanation for it.
Searching meta turned up a few questions on this (e.g. Why I got only 2 reputation for upvote [duplicate], Only received 2 rep for an upvote) but none are relevant as I have not reached the reputation cap. Also, I have not accepted any answers and I don't get +2 for edits anymore.
Is this a (small) bug or am I missing something?