Ditto, I've noticed that all the large files seem to have the sparse attribute in the tooltip,
Physical Size does not seem to represent size on disk.
I have a file
Explorer tells me Size 64.1 KB and size on disk 0.
Spacemonger lists size as 64.1 KB but Physical Size as 8.0GB
Looking through quite a lot of my files are size on disk 0 that have this 8.0Gb physical. This seems to be an overflow bug, space monger not handling zero sized files?