@Nicole1913 I somewhat agree with her that the photos and the description are a bit misleading. You mention that the dining room table seats 8, you show 6 beds, 3 of which could easily sleep 2 people.
The other part of the problem is with ABB, in that they allow you to set a max but they don't allow you to break that number into adults and children which is I guess what you'd prefer.
Also, some of this confusion is just a terminology issue, if you require that guests have to message you to book then you don't have any Instant Bookings but rather you have a Request to Book that you don't need to Cancel but which you will need to Decline.
So, if you'd be willing to host 4 adults and 4 children then you could set your max to 8 and yes, you occasionally will have to tell someone who hasn't read well that you will not take 8 adults.
OR you can set your max to 6 total and then you'll only get requests for people who are purposefully trying to pay for a smaller place and house more people. IF you go that route then I'd borrow a page from @Emilia42 and not showcase all 4 beds in the bunkroom.
The third option is "allow" parties of 8 but make the charge for guests 7 &8 be prohibitively more expensive.
But none of that really helps you with how you'll handle the extra sneakers.
and to your other question, if your max is 6 then the system will not allow any additional charges bc it will not allow guests to be added above 6. And if your max is set to 6 and you get an inquiry from someone who is looking to house 8 then they are purposefully searching for listings that don't fit them