Door Lock Question" Lock if no door is opened"

I just got my 201 5501 GT. love it, however, I have a question. On the iDrive door lock menu in settings there is an option for "Lock if no door is opened" WHat does that mean/

Thanks

You unlock the car, then for some reason within a time period, never open a door (I think the time is in the order of a minute or so, but don't remember exactly), the vehicle will relock itself. If you open a door within the timeout, it will stay unlocked until you lock it again.

Thanks