A division of the space above or below a lot, or partially above and below a lot, having finite width, length, and upper and lower elevations, occupied or to be occupied by a use, building or portion thereof, group of buildings or portions thereof, accessory buildings or portions thereof, or accessory uses. An air space lot shall be identified with a separate and distinct number or letter on a final subdivision map or parcel map recorded in the office of the County Recorder.