The way this metric is calculated is based on the time from when a TICKET is CREATED as a NEW ticket, until it is ASSIGNED to a GROUP or an AGENT.
1) Ticket is created by END USER (comes in with a status of NEW, not in a GROUP or assigned to AGENT yet)
2) An agent ASSIGNS the ticket to ANY GROUP or ANY AGENT
The time BETWEEN the above two actions = Average First Assigned Time
So unlike Average Escalation Time, this metric is based off when the ticket is first assigned to any group or any agent -- and NOT when an agent CHANGES the GROUP to another group.