We currently selected default session time out for 2 hours

Lockout effective period for 30 min

However, every 30 min, an pop-up window will ask whether we want to continue working or logout.

Therefore, I assume it is controlled by the Lockout effective period. But what confuse me is the Lockout effective period can only select 15min, 30min, 60min or never (must reset by admin); but session time out can select a longer time. What are they actually for?

2 hours auto log out would be the best for us. How do I control these two options to achieve this? 

Any information would be very much appreciated!