Originally Posted by lovelypingu
there isn't exists any other mount point for that partition.
From the thumbnails, I see that is your root filesystem. It contains mount points I can see for /boot, /home2, /home3, and /tmp, and undoubtedly has several more not shown (/proc, /dev, ...). Any of those mount point directories in the root filesystem could contain files that are hidden from du
There is a way to access what might be hidden under those mount points.
mount --bind / /mnt/tmproot
du --max-depth=1 /mnt/tmproot
Large numbers for any of your mount point directories show you where data is hidden. You can access that data under /mnt/tmproot to copy it elsewhere or delete it if, for example, it turns out to be an old version of what is now stored in /home3 on /dev/sdc1. After you have finished cleaning out that hidden data, you should