SEP11 randomised scans

A question about randomised scheduled scans in SEP11:

I have a server which takes six hours to complete a full scheduled scan of all its local drives.

If I set the scan duration in SEPM so that the scan duration is limited to 2 hours, that will leave some data on the server unscanned.

What will happen the next time the scheduled scan starts - will it start from the beginning or pick up where it left off?

Thanks