Difference on root size between the Dashboard and Disk usage

Hello,

Information between the disk information in the Dashboard and disk information in the Disk usage are different.

Expected feature: The same information to be displayed
Occured feature: The root partition has one size in the Dashboard and another size in the disk usage...

Capture d’écran 2015-11-09 à 13.48.46.png1920x1080 1.07 MB

Capture d’écran 2015-11-09 à 13.50.12.png1920x1080 1.17 MB