Internet Worm protection update confusion

NAV2008,   Windows Vista with Vista Service Pack 1, all updates current 

 

Received an internet worm protection update last night (11/24/08).

When I looked in the Worm Protection log  it appeared to be from 11/21/08 

Internet Worm Protection Signature File 1234 signatures

Version 20081121.001

Internet Worm Protection Engine version 4.1.0.61 

I had received this same file 11/21/08 with the same information. Not sure why it would send out the same one twice and why one coming 11/24/08 would be dated 11/21/08 

Anyone able  to enlighten me as to why I would get the same file a second time, but 3 days later??

Did I not really get it the first time even though it was listed in worm protection log?