OK what version of security centre if 11.* well Scheduled scan start when it sees teh CPU at less than 10% usage for 10 minutes straight. If it cannot get a 10Min period it will force a start after 2 hrs of trying. If you turn off the PC before then teh 2 hrs setting resets.
Set scan for a time you will have the laptop on. Also I can instruct you as to how to force the scan to strt immediately on time if you wish. This issue fixed in 2012 beta version.
You are exactly right! If you set a scan at 4 AM in the morning and the PC was not ON by that time. Schedule scan will initiate a scan the next time the PC starts .
This is not an issue, this is by design,