How to set SAP idle session time out

how to set SAP idle session time out  rdisp/gui_auto_logout

Parameter Description

You can define that inactive SAP GUI users are automatically logged off of an SAP system after a predefined period of time. The parameter configures this time period.
Automatic logoff in the SAP system is deactivated by default (value 0), that is, the users are not logged off even if they do not execute any actions for a longer period of time.
Application Area
Parameter Unit
You can specify the value with or without a time unit. If you do not specify a time unit, seconds is used as the unit. Otherwise, you can specify M for minutes, H for hours, or D for day. There can be spaces between the value and the unit.

rdisp/gui_auto_logout = 400

is 400 seconds or which ever time you need you can assign to the parameter.

400, 400 Seconds
5 M, 5 Minutes
1H, 1 Hours