On the Editions model, a license is consumed if a user has been active at least once over the past 90 days.
Even users that have been archived or deleted are considered an Active User and will consume a license if such users have been active at all (i.e., accessed a service or Service Tunnel or checked in on a device that has an ITP policy associated with it) within the last 90 days.
An Active User is one of the following: