No problem, welcome to the forums.
That is most strange, all I can thing of is if you kept stopping it then it didn't complete, so the next time you restart it would try the boot-time scan again, this is speculation on my part.
If you happen to have scheduled a boot-time scan and you don't want it to run, I believe if you go in again to schedule a boot-time scan it will ask if you want to cancel the one scheduled.