This booking platform will not let you account for any more guests then you list as your max. For example, if you list your place is suitable for 4 guests, then the booking cannot be submitted for more then 4 and it is impossible for the system to charge for an “extra.” You will only appear in search results where the guest indicates 4 or less people. You could work around this by adding a clause to your house rules and charging an additional amount through the resolution center. I think this is effy because technically the confirmation would still only include 4 guests. And you would be relying on guest to actually read your listing to discover this info.
Personally, I think it is best to stay consistent. If your place sleeps 4, in real beds, then list for 4. If you increase this number to 5, there is no way to prevent groups of 5 adults from seeing your listing in their search results and trying to book.