Specify the period of inactivity before Windows transitions to sleep automatically when a user is not present at the computer. ...

Specify the period of inactivity before Windows transitions to sleep automatically when a user is not present at the computer.
      
If you enable this policy setting, you must provide a value, in seconds, indicating how much idle time should elapse before Windows automatically transitions to sleep when left unattended.  If you specify 0 seconds, Windows will not automatically transition to sleep.

If you disable this policy setting or do not configure it, users can see and change this setting.