To RU5?
If so, it's normal
There is a new way to compress content
To reduce hard disk space, Symantec Endpoint Protection Manager now stores only the most recent full set of virus definitions, plus the deltas for previous versions. Storing the deltas reduces delivery time and network bandwidth, and improves disk storage requirements on the management server by 65% to 80%.
http://www.symantec.com/docs/HOWTO101747