This isn't really a mayor bug but it's sort of confusing and...well...even if it's small it's still a bug, so I better report it.
Something's wrong with the sort by filesize function...
A file, 3,91gb, is considered smaller than a 30kb file...A 1,73gb file however is considered bigger than the 30kb file (meaning the 1,73gb file works correctly, the 3,91 doesn't).
Therefore, there gotta be a bug somewhere...maybe a/some certain size/s is not being sorted correctly. Take a look at it somewhen...or just ignore it as it isn't really important...