from and to select handles by when the agent answered. timezone is an IANA name, default UTC. Filter with team_id, policy_id, user_id, or direction (inbound, outbound).
aht_seconds is (talk_seconds + hold_seconds + after_call_work_seconds) / handles. Only finished handles count: the agent has left the call and their after-call work has ended. A call two agents handled counts once for each. over_target_rate is over_target / graded, where graded handles had an AHT target when the agent answered. target_seconds is the target when every handle in the range had the same one, otherwise null. See Average handle time.