Disk space counted twice on root folder?

Edit: SOLVED thanks to r00ty !

Hello, I have this weird issue that my Debian 11 will tell me the root folder is full, while I can only find files for half of the accounted space.

df -h reports 56G while the disk analyser (sudo baobab) only finds 28G.

Anyone ever encountered this? I don't have anything mounted twice.... (Not sure what udev is). Also it does not add up to 100%, it should say 7.2G left not 4.1G

df -h /dev/sda* Filesystem Size Used Avail Use% Mounted on udev 16G 0 16G 0% /dev /dev/sda1 511M 22M 490M 5% /boot/efi /dev/sda2 63G 56G 4.1G 94% / /dev/sda4 852G 386G 423G 48% /home

Edit: my mtab

Edit 2: what Gparted shows