An 'AVAILABLE' course is one in which the instructor has made Available for students to access.
A 'Student Seat' is defined as access to the system by a single student in connection with a single SIS class. (e.g. access to the server by the same student in connection with two classes constitutes two "seats").
Unique student users are all users that are registered for an UNI academic class for that specific semester on the census date.