The dashboard in the Advanced Threat Protection (ATP) UI is showing more endpoints under Total Endpoints than what's listed in your Symantec Endpoint Protection Manager (SEPM) environment.
Refer to screen shots in the Error Message section.
Symantec is aware of this issue and will update this document when a solution becomes available. It is not necessary to log a support case on this issue. Please subscribe to this article to be notified of any updates.