I also have had this problem several times. I have decided to message the guest asking them to adjust the number. I explain that I leave bottle water, towels, and baked items based on the number of guests on the booking. I would hate for them to not have enough towels etc. They’ve all apologized and didn’t realize that only 1 guest was listed. So it would be nice if AirBnB could somehow make that clearer for guests. Thanks for bringing this to AirBnB’s attention.