How do I give a discount to a guest due to inconvenience?

Location of the parking was described on Booking as "at a location nearby", but it is 300m away from apartment.

Guest is complaining that he did a reservation thinking that parking is next to the apartment.

I would like to give small discount to avoid bad review due to this. (actually "at a location nearby" was set by booking, but I do not know is it possible to change this)