A ClearDB Documenter license relies on the two metrics: a number of users and a number of DBIs (database instances). Each user license is granted access to three unique database instances. Generally, these are production, test and dev databases, or any other instances defined by user.
The instance is considered registered in ClearDB Documenter, when there's a first report generated on that instance. A user can generate an unlimited number of reports on a registered instance.
Please note: a trial license supports 3 unique Oracle database instances and 1 concurrent user.