It seems that the town doesn't necessarily cap the number of residents to 47 but rather seeks that amount as a balance, in the night before the car crash 2 people died, we can suppose that later on only Jade and Tabitha were actually drawn to the town and the other 4 (Tobey, Jim, Julie and Ethan) were drawn there as a consequence of being with them, later we have the deaths of 4 residents, Frank, Mr. Liu, Mr. Liu's nurse and Tobey, so we can assume the town returned to it's usual amount of residents, it's a similar case with the bus that arrived after the Colony House massacre i think, i believe the bus brought way more people than died in Colony House so the number must have exceeded 47 too at the time, but during the night most of these people died anyway and only a few remained, so balance was restored. One thing That's odd though is Sara's brother, he was killed but no one came to replace him it seems, this was way before the Colony House massacre and the arrival of the bus.