Unfortunately, for right now there is no way for the client to know this... There is a way, but it involves the registry... so for end users, it is recommened there is no way.
There is a discusion on this here:
https://www-secure.symantec.com/connect/forums/centralized-exception-configured-console
An extract here:
To know whether the centralized exceptions are getting applied to the client/agent?
To check the policy serial number at the server
Login to the Symantec Endpoint Protection Manager console
Select the Clients button on the left margin
Select the client group that contains the client that has the issue
Select the Details tab in the right hand pane
Copy down the policy serial number.
Example: E0C4-01/09/2008 14:39:16 311
To check the policy serial number in use at the client
Launch Symantec Endpoint Protection from the System Tray icon or the Start menu
Select View logs button
Select the View Logs button to the right of Client Management and select the System Log
Select the Filter from the main menu and select Show All Logs
Browse for the most recent entry labelled "Applied new policy with serial number..."
Compare the serial number with the serial number shown in the Symantec Endpoint Protection Manager console
Example: E0C4-01/09/2008 14:39:16 311
If policy serial number are same on both the side than the policy is implemented successfully
Please check this link also
Can no longer see the Administrator-defined Exceptions Tab on Clients after migrating to Symantec Endpoint Protection MR3 or MR4
http://service1.symantec.com/support/ent-security.nsf/854fa02b4f5013678825731a007d06af/73a278b5de8e0af9882574d40064cd2c?OpenDocument
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