@Susan963: It is fairly common for guests to misrepresent the number of guests actually arriving. If you charge additional for more guests then you can send a resolution request for the additional guest. It may or may not get paid.
As the years have past we have found that more and more guests provide less and less information about them when booking. Many guests simply put, "Thank you," or even just, "Hi."
@Susan963 I have it in my house rules that I must know the names of each guest. And I have an additional rule that I don't allow any visitors or people that are not listed in the booking. It might be worth updating your rules to something similar & sending the house rules to the guest when they book. It may stop people bringing an additional person & not telling you because they want to avoid paying the extra charge.