The full user license is counted when the role assigned to a user record is using any center type except the following:
Advance Partner Center
Customer Center
Employee Center
Partner Center
Vendor Center
So in order not to use a full user license, you need to assign users only to these center types. NetSuite Specialized Centers are listed in SuiteAnswers article ID 109219 (access the links for more details) and if you assign a user to these centers, this should not be counted against Full user licenses . IMPORTANT: If a user record has both employee center role and full user license role this will be counted against the full user license.