If your policies include a fee for each additional guest, in my experience, airbnb will enforce this.
I had a family of 4 make a reservation. they asked if one additional person could come, i was reluctant but it was a spouse so I said ok and did not charge a fee. then they asked if 3 more people could come. sorry, the place just cannot hold that many people. the guest said ok, I've booked another property nearby we will spread the family out between the 2 locations.
after they checked out, my neighbors said they counted at least 8 people. so they lied. I wrote all of this up and requested a resolution with the full fee for the extra people. to my surprise, the guest agreed to pay the fee and apologized. The payout was sent to my account that same day. I chose not to mention this in my review, since it all worked out and I felt that the guest had done the right thing.