Reminding once again: The Ultimate license policy always implies concurrent, that is, simultaneously working users.
Which is different from named users preferred by our foreign colleagues when the user limit is defined by the number of system logins irrespective of how many of them actually work at every specific time.
Licenses lease may be paid for any number of users and any time period in days. You can do it in your user account.
A license in reality is a file.
The license file contains information on the number of concurrent users and license period duration. Initially you get the "general" license for 12 users valid without any time limitations.
Users of paid support packages are given a named license linked to a particular system installation with unique details. Once the license lease for extra users is paid you will get a new license file to be uploaded to the server.
While paying you can set the date the lease period is counted from (by default — once the payment is effected).
New licenses will be used within the specified time frame.