Yes A time is from the time he wakes till he sleeps. In reading your EASY, I see it only as 2 hours.If his naps are always irregular and short, there is no harm in giving him a 4th nap. If they are not taking the full naps, you can always do more naps. I see your proposed CN from 0530-0615 with BT at 8pm, this will work.
Let us know how it goes.