Five doors x 2 CC/door = 10 CC.
That leaves five other CC "doorless", making 15 in total.
So where lies your problem, MissM?
There are 12 doors on 747.
My, and many other crews problem, is that we have more or less been brainwashed both in training and onboard to NEVER leave any door unattended. You could always leave your door as long as you were no longer away than five seat rows.
BA has now changed their mind and don't see a problem with numbers 5 and 10 leaving their doors some 15 seat rows away for safety demo. BA Safety Department replied and said that passengers will have paid attention to the safety demo and will also remain seated should an emergency occur.
Do you honestly think people will stay in their seats like well-behaved children if there's smoke development in the cabin? Good luck getting to your door.
There LIES the problem.