XPS13 - Hard drive full - 40GB hidden

Hi All

I purchased a Dell XPS13 and it has only 4GB left free. No pictures, movies, music on the computer. 

1. If check properties under C: -->   Total Disk space: 92.9GB ; Windows: 25.3GB ; Users 13.1GB

2. If look under disk management --> OS C: 92.9GB  Recovery: 18.25GB  Hibernation: 8GB

BUT when use disk analyzer tool 

Treesize:  C: 63.4 GB     Windows 26.1 GB    Users 13.4GB

Spacesniffer   C: 61.5GB   Windows 25.4 GB  User: 13.1 GB

My question is that why am i not seeing around 30GB of disk space. I have hardly any data on this computer and already running into diskspace issues.

Thanks for your help