Puzzling extra stuff being copied
 

Sorry I was not sure how to best word the heading.

Anyway so I did a smart update, and a few days later I ran it again and surprisingly it said that it copied over another 5GB of data, which I'm pretty sure did not get added to my HD.

So after that was done I immediately did another smart update and a further 850Mb was copied over, and this time I'm certain that nothing was added. All programs were shut down.

Is there some logical explanation for this?

Thanks.

Your drive is constantly changing. Logs (which can be large) are being added to, email indexes are changing, etc. So, it's quite unlikely that two copies will copy nothing. This seems pretty normal...