Please refer to the HDX Administrator's Guide, found here The same guide applies for all the HDX series products.
Screen Saver Wait Time
Specifies how long the system remains awake during periods of inactivity. The default is 3 minutes. If the system requires users to log in, the screen saver timeout also logs out the current user.
Setting this option to Off prevents the system from going to sleep. To prevent image burn-in, specify 3 minutes or less.
Note: The screen saver feature is disabled during the setup wizard. To prevent image burn-in, complete the setup wizard promptly.