Hi @Shannakay0 🙂
When I try to book your place the price is the same if I book for 1 or for 4 persons. You need to change settings so it says 60$/guest after first guest. You can change the settings under price settings and then choose extra charges - extra guest.
If the reservation is a confirmed reservation I would personally as a host eat the mistake and let the guest stay for the price they paid. It is not the guests fault the listing wasn't updated with the correct prices. You need a good review as a brand new host - that’s the most important thing. If you don't feel comfortable with instant book yet - turn it off for a while. Then you will get requests from guests and will be able to see mistakes before a reservation is confirmed and also you got the change to communicate a bit with the guest to see if it a good fit for you and the guest.
What I would do is nothing but greet the guest. Asking for more money after a booking is confirmed is not okay and it could easily lead to a bad review. Cancelling out on a guest is also not a good idea - you will get penalized 50$/100$ fee and it will say on your profile that you cancelled a reservation on your listing. So best option is to eat the reservation and update your settings :-).