If the request has not been approved by you, you may inform the guest that you need them to reply by a certain time (tell them your deadline for a reply is a couple of hours before the 24 hour deadline for your decison.) Tell them if you do not receive clarification by that time you will decline and they can resubmit a request after they decide what they want to do and communicate with you to your satisfaction.
If it was instant book then they have a reservation. You can message them that their reservation is for however many they booked for and that if they arrive with more than that many people they will have to send the others away to a different place.
It is not your responsibility to make a correct reservation for them, nor is it wise to accept a reservation that is not clear to you unless you are willing to accommodate how ever many show up. People who fail to communicate before they even arrive are a big red flag!