If I understand you correctly, you want to reduce the number of content revisions on the clients.
If you are running SEP 12.1, you cannot reduce anything. There is only one version by default.
For SEP 11.x, follow this document:
Configuring the number of content revisions kept by the Symantec Endpoint Protection client
http://www.symantec.com/docs/TECH103956
The number of content revisions will decrease as soon as the next content update happens. (If it does not work at once, stop and start the SEP 11 client service: Start > Run > smc -stop / smc -start)
Unfortunately, there is no setting at the SEPM console to decrease the content revisions at the clients.
However, if you want to reduce the number of content revisions on the SEPM you can follow Ashish Sharma's solution. The number of content revisions will decrease almost immediately. But three content revisions on the SEPM are too tight in most cases. With a long time line of content revisions, the SEPM is able to create small update delta files even for clients that were offline for some time.