Install Timing

Hello -

I notice that if I uninstall an update, it seems that almost immediately the
same update is downloaded again. Is this correct or expected?

As far as I know, downloading of updates is random and occurs every 22 hours
by default, so I am not sure why this would happen.
Can someone confirm this and hopefully explain it?

Also, if a machine has been off for a length of time (lets's say a week) it
appears to download any new updates immediately. I realize this is a good
thing, but it is off schedule so I'm hoping someone can also explain that.

I need to explain Windows Updates to our CSO and I realize there are a few
things that I'm not sure of. Of course, pointing me to a document that
explains the exact behavior may be even better.

Thanks.