To set the number of simultaneous NRT or live chats that the user can handle you need to tick the corresponding box and fill in the number you desire in the field. To get to these settings, you need to go to "Users & Groups" and select the user from the list in the "Users" subcategory.
The set numbers will then show in the list under Live chats and NRT chats.
In this example, the user is set for 15 simultaneous chats and 28 simultaneous NRT chats.
In the case of unlimited chats set or box unticked, the user will be able to receive unlimited amounts of simultaneous chats. This is how it will look at the summary for such a user.