what are the apartment numbers for those 7?
SELECT DISTINCT T2.apt_number FROM Apartment_Bookings AS T1 JOIN Apartments AS T2 ON T1.apt_id   =   T2.apt_id WHERE T1.booking_status_code   =   "Confirmed"
apartment numbers refer to apt_number; DISTINCT is used to select unique apt_number; JOIN is used to combine rows from two or more tables based on a related column between them; booking_status_code = 'Confirmed' filters apartments with confirmed bookings;