In order for you to set the Idle countdown for a user.
Step 1:
Login to CometChat Admin panel using credentials.
Step 2:
From left menu Click on "Settings->General".
Step 3:
Search for "Advanced Settings"
Step 4:
In this section search for "The number of seconds after which user will be considered as idle:".
Step 5:
Changes the value of the option.
Step 6:
Click on "Update".
Step 7:
Click on "Clear Cache" from the left menu.
Step 8:
Clear Browser Cache.