Have you read the official documentation?
See https://www.traccar.org/documentation/user-management/
In the part where it is to mark admin, do not check, just put a number of trackers / devices so that he can register devices, inform a number of users if you want this manager to register users.
Yes Anton I have read the documentation but there is NOT ONE WORD about how to create a manager. Its a pity that the documentation is not as super as the software because traccar is really good
If user limit is set to 0, it means that user is not a manager. The difference between manager and regular user is in their user limit value. Manager has limit not equals to 0.
How do I create a manager in the server?