Group and Owner of Directory Change on Mount

■ whoami
root
■ ls -l /mnt
合計 14
drwxrwxrwx 4 root root 4096  6月  7 21:31 G
drwxrwxrwx 8 root root 4096  7月 14 04:59 H
drwxr-xr-x 1 root root 2048 10月 21 02:13 iso
drwxr-xr-x 2 root root 4096 10月 26 14:03 usb
■ ls -l /dev/sdf*
brw-rw---- 1 root disk 8, 80 10月 26 14:45 /dev/sdf
brw-rw---- 1 root disk 8, 81 10月 26 14:45 /dev/sdf1
brw-rw---- 1 root disk 8, 82 10月 26 14:45 /dev/sdf2
■ mount /dev/sdf1 /mnt/usb
■ ls -l /mnt
合計 14
drwxrwxrwx 4 root  root  4096  6月  7 21:31 G
drwxrwxrwx 8 root  root  4096  7月 14 04:59 H
drwxr-xr-x 1 root  root  2048 10月 21 02:13 iso
drwx------ 6 userX userX 4096 10月 26 14:36 usb
■ echo "Why does the group:owner pair change???"