I tried
greedy@algorithms:~$ ls -l /
total 2097292
drwxr-xr-x 2 root root 4096 11月 28 15:55 bin
drwxr-xr-x 3 root root 4096 11月 28 16:34 boot
drwxrwxr-x 2 root root 4096 5月 8 2018 cdrom
drwxr-xr-x 20 root root 4540 12月 2 00:40 dev
drwxr-xr-x 135 root root 12288 12月 1 07:32 etc
drwxr-xr-x 4 root root 4096 11月 27 20:53 home
what does the second column and the 7th column mean? especially the large number 135?