@Dana-and-Vance0
Have they sent a booking request? Unlikely as it would be against your booking condition - so I believe there is nothing for you to decline.
What you can do is go to your Availability Settings. Click on Reservation Requirements and then Add another Requirement. This will allow you to put in a bespoke set of dates and set the minimum night stay. So if the night was for example 3 May, then set the dates 1-4 May and the min number of nights 1. Then message your guest and ask them to submit a booking request for the 1 night