With regard to maximum number of persons, I do not believe it is referring to the number of berths, but simply the maximum number of people who can be on board, even for a day sail.
This from a charter captain whose large catamaran was approved to carry up to 36 people, which he did for day sail charters in the Caribbean.
One of the frightening scenes last winter in the Florida keys were the number of boats that were dangerously overloaded with people including very small children out for the day or weekend. Many of these were chartered small boats. I sometimes think that the Coast Guard ignores these overloaded boats as a form of population control