Erased 32GB USB flash storage with Disk Utility's "Secure Erase" feature, one pass of zeros. Disk Utility now reports that there is only 26GB of my drive available. Not sure what is going on here, but I'd like to know where my 6GB of space went.
Update: Zeroed the drive using DD, created new partition using Disk Utility, resized the partition and created a new one. It appears that for each of my partitions created, 6GB of the available space is taken up by something. The hidden files (Trashes, Spotlight, and fseventsd) do not account for this usage. This is really baffling and annoying, and any clue as to what is happening would be very appreciated.
Edit: Pictures to clarify:
Problem occurs on more than one drive, I think it has something to do with either journaling or local time machine backups.