10 Client connected to SEPM.
Only 10 SEP client if you will be add more client,Please see below impact.
if you are running the SEP 12.1 Enterprise Edition, then there would be no virus definitions update issues.
For 12.1 Enterprise Edition, over deployed clients work normally. However you would keep receiving an alert notification for the same.
For 12.1 SBE, over deployed clients cannot download definitions. Plus there is a Grace count.
Types of enforcement
When the license goes out of compliance the Symantec Endpoint Protection product goes into enforcement mode. There are two types of enforcement
1) Hard Enforcement: SEP 12.1 Small Business Edition
- Content update downloads stop for both server and clients.In Small Business Edition it's 1:1 mapping with CAT server.
- UI changes and log notifications are started.
2) Soft Enforcement: SEP 12.1 Enterprise Edition
- Content update downloads continue from all the sources.
- UI changes and log notifications are started.
https://www-secure.symantec.com/connect/articles/sep-121-and-license-concept