So now you have the number of passengers and bags in the cargo hold (along with any other cargo).However, the initial load is already calculated from dispatch which is taken from the known number of passengers already booked, number of bags and cargo) so you know an approximate calculated weight so fuel can be ordered.
In real life the gate agent gives the pilots the load sheet before closing the door which gives the total souls on board and from that you get your weight and balance (190lbs per soul) as well as the number of checked bags (assuming max allowed 35-50 lbs per bag depending on airline policy).
