Question about chat_agent_sessions.engaged_secs

Content

The data dictionary describes this column as "The total time (in seconds) the agent spent chatting during the session."  

But what does that mean? Is that the seconds that the agent is physically typing? Or is it the time spent with an active chat, whether they're responding or not? How does it work if they're taking two chats concurrently? Is it doubled?  

Our agents can take up to two chats concurrently, and I want to be able to show how much time out of their available time that they're in an active chat, not in wrap up and not waiting for chats.