Limiting maximum duration of user inactivity
Similar questions: How to force the log out if user is inactive a certain period of time? How
to prevent unauthorized person working in some user’s account once he’s absent
from the workplace?In the 
go to 
page and scroll down to the inactivity
duration section
If you wish to set up this duration period –
activate the “Force users to log out” button and indicate the desired time in
minutes: