@Elena5007
If it's an inquiry, then all you have to do is ask them to submit a request to book for 4 guests.
If it's an actual request to book, you'll have to get the to cancel the request and resubmit as @Helen3 suggests.
If they have no reviews and are new to Airbnb, it would be up to you if you want to accept a request to book when they correct the number of guests. Airbnb says you have to decline "a lot" of bookings for it to affect you in search results. Not sure what the mean by "alot" but I don't think a few is an issue.
How A Guest Can Withdraw a Trip Request
https://www.airbnb.com/help/article/90
The guest must either withdraw the trip request and submit a correct one, or you have to accept or decline the original trip request within 24hours.