With the September 2016 update, the Streetpass Mii Plaza is said to be able to hold 100 Miis in the queue, as opposed to the maximum of 10 it could before, as long as the user has purchased the Premium update.
I do have the Premium update, but the Plaza seems to still have a maximum of 10 Miis in a queue at one time. It filled up and wouldn't accept any more until I "welcomed" them.
A new icon has also appeared and selecting it says that I can have people wait in there but there is no indication about how I could do this.
How does the new maximum of 100 Miis work?