Not that this really matters to me, but the reason isn't obvious, so I'm curious.
In the "Achievements" tool in the page header it shows -5 for yesterday on a 10 month old answer.
Viewing my profile in various forms, I can't find -5 listed.
I've seen -1, -2 and -15 before, and understand how those values could come from, but how do you get -5? This page of the help center, doesn't give me clues either.
The answer I'm referring to is this one.