When using User Mode clients, the number of licenses required is the number of computers where the Symantec Endpoint Protection (SEP) client is deployed, as described in the article Do User Mode Clients in Symantec Endpoint Protection 12.1 Require Additional Licenses.
However in SEP 12.1 RU2, seats used are incorrectly counted as the number of users that have logged on per machine which may lead to warnings that SEP has been over deployed.
There may be a warning that SEP has been over deployed although there are more licenses than installed SEP clients.
This problem is fixed in Symantec Endpoint Protection 12.1 Release Update 3 (12.1 RU3). For information on how to obtain the latest build of Symantec Endpoint Protection, read ‘Obtaining the latest version of Symantec Endpoint Protection or Symantec Network Access Control’
SEP 12.1 RU2 / User mode.