chmod inc not change

I tryin and tryin change that chmod inc non-writable but not can change
what is that chmod number what is non-writable?

Directories       Current Level       Desired Level
inc                      Writable                Non-writable

If PHP is running as CGI, it's 555. Otherwise, it's 755. You may need to wait a few seconds for the script to register the change.

Ok thank you once again.