I had an album with 2 media. I removed the media and then the album or maybe I removed the entire album including the media, I don't remember. The thing is that right now I have 0 albums and 0 media however on my profile I see this: Albums: 0 / Media: 1.
If I enable myself to see deleted albums/media I can see that in fact the album and the 2 media are deleted.
On the Gallery Statistics block I see:
Disk Usage: 45.3KB
Maybe this is related to this? I don't know.