I think I found an error in ISPConfig 2.2.0.
In statistics I read something like that:
Speicherplatz gesamt: 4096 MB
You see "verbraucht" is not correct. It should be "1.20G".
Here is the output of "du -h -max-depth=1":
You see: The output of du is correct but the summation in ISPConfig is wrong.