Mailboxes add to only 10GB, why is priv1.edb 20GB after defrag?

I have an Exchange 2003 SP2 Ent Ed server.  Overkill for the 30 users and mailboxes we currently have.  I took the store offline and performed a defrag with eseutil.  At the time the priv1.edb was 32GB.  After the eseutil defrag it was 20GB. The priv1.stm file is 4GB, reduced from 5GB.  The pub1.edb and pub1.stm files are only about 70MB cumulatively.

When I expand the Mailboxes (under the Mailbox Store in Exchange System Manager, I can see the size of every mailbox.  Cumulatively each mailbox adds to a total of about 10GB.

Why is the Priv1.edb file still so large? Could it have anything do do with the # of items in a mailbox?  In the past I thought maybe database integrity was the issue but the edb files always pass integrity checks. What else could be holding space inside the .edb database file? 

 Thanks,

MrMMills

Houston Texas

Have you exmerged mailboxes into this store?

also this may be relevant

http://support.microsoft.com/kb/812232 

also http://www.exchangenewsgroups.net/group/microsoft.public.exchange.misc/topic6856.aspx

although I'm not sure how you would use Performance Monitor using the MSExchangeIS Private
and MSExchangeIS Public objects to show it?