But the second partition (main OS) has 'Lost and Found' and another file that says it's empty, but 2.4gb is used.
$ ls -al загалом 48 drwxr-xr-x 9 root root 4096 2000-01-01 02:04 . drwxr-xr-x 9 root root 4096 2011-05-05 12:18 .. drwxr-xr-x 2 root root 4096 2011-03-24 00:27 common-data drwxr-xr-x 2 root root 4096 2011-03-24 00:32 .images drwx------ 2 root root 16384 2011-03-24 00:26 lost+found drwxr-xr-x 8 root root 4096 2000-01-01 02:05 .overlay-ai-os drwxr-xr-x 8 root root 4096 2000-01-01 02:00 .overlay-android drwxr-xr-x 9 root root 4096 2000-01-01 02:04 .overlay-chromium drwxr-xr-x 10 root root 4096 2000-01-01 02:00 .overlay-ubuntu