Large (20gb) Disk Space Difference

[Sorroko]

Hello,
I am very confused as to what disk space to trust,
Finder reports 52.22 GB available...
however...
Disk Utility and the "df -h" command report only 28 GB available

Thats a huge difference, 20gb difference. It seems like Finder isn't taking into account a folder hidden somewhere in my system (maybe with backups). However TimeMachine is off, and in About This Mac backups are reported as Zero kb. I wonder if you can help me try to find the cause of this lost space.

Thank you, any suggestions are greatly appreciated.
- Ryan