The habitable area of residential use on each of the second and third floors shall be no greater than the gross leaseable area of the non-residential use located on the first floor. Balconies, decks, porches and open, common stairs are not considered in the calculation of the residential habitable area. Semi-enclosed parking, residential storage and refuse areas, common stairs, ramps and other common areas, shall not be included in the calculation of the gross leaseable area.