Disk usage is different than what reported by df on the Ubuntu

Environment

• OS: Ubuntu 20.04
• Node version: ($ node --version)

v12.22.6

• gtop version: ($ npm info gtop version)
• 1.1.2

Description

what df reports:

Filesystem Size Used Avail Use% Mounted on udev 3.8G 0 3.8G 0% /dev tmpfs 771M 1.9M 769M 1% /run /dev/sda8 201G 92G 99G 49% / tmpfs 3.8G 0 3.8G 0% /dev/shm tmpfs 5.0M 4.0K 5.0M 1% /run/lock tmpfs 3.8G 0 3.8G 0% /sys/fs/cgroup /dev/loop1 128K 128K 0 100% /snap/bare/5 /dev/loop0 56M 56M 0 100% /snap/core18/2246 /dev/loop3 62M 62M 0 100% /snap/core20/1242 /dev/loop2 56M 56M 0 100% /snap/core18/2253 /dev/loop5 219M 219M 0 100% /snap/gnome-3-34-1804/72 /dev/loop4 62M 62M 0 100% /snap/core20/1270 /dev/loop6 219M 219M 0 100% /snap/gnome-3-34-1804/77 /dev/loop7 248M 248M 0 100% /snap/gnome-3-38-2004/87 /dev/loop8 65M 65M 0 100% /snap/gtk-common-themes/1514 /dev/loop9 55M 55M 0 100% /snap/snap-store/558 /dev/loop10 51M 51M 0 100% /snap/snap-store/547 /dev/loop11 66M 66M 0 100% /snap/gtk-common-themes/1519 /dev/loop12 43M 43M 0 100% /snap/snapd/14066 /dev/loop13 14M 14M 0 100% /snap/universal-ctags/552 /dev/loop14 44M 44M 0 100% /snap/snapd/14295 /dev/loop15 15M 15M 0 100% /snap/universal-ctags/749 /dev/sda6 2.7G 158M 2.4G 7% /boot /dev/sda2 96M 31M 66M 32% /boot/efi /dev/sda9 550G 92G 431G 18% /home tmpfs 771M 648K 771M 1% /run/user/1000

what gtop reports: