Trash empties nonexistent files?

I emptied my trash and it was taking forever. For ten minutes it said it was emptying files from Dropbox -- over 200,000 of them by the time I left the room.

The thing is, I only have the minimal (free) subscription to Dropbox. I rarely use it and only have 4 or 5 files there which don't even add up to 1MB.

When I came back the emptying was finished, so I don't know what the final number was. This is awfully weird. Does anyone have any idea about what was going on?