I've had the maximum of 100 available comment flags for some time. It's been my observation that the number of available flags is decreased by one for each outstanding flag; however as flags are handled the available flag count goes back up.

A bit ago I flagged a comment and noticed my available comment flag count is not 100:

The only flag I have pending is the one I just cast:

I'm pretty sure the available flag count hasn't gone down because of declined flags, since the last comment flag I had declined was on Jan 27 2018. I don't have any other type of flags outstanding either, in case that matters.

What could be the reason I'm "missing" 12 comment flags? Did I do something to make this happen?