hi #32798 it's like the number is a cap of some type
I came across that this could be due to small hole air exposure, so a fermentation of sorts. Not always appealing to the eye for most, but it isn't damaging I don't think unless it's gone long as mold appearing... gray, hey. Which is often at the stem, least sealed if not accidentally slit elsewhere or even thin part of shell, where you could locate it too from poor purous results. So warning is highest on ending scrapes, if that helps!
I hope my memory is from information and not a waste of time,
Carolyn