The total of all gross floor area of a building within interior walls, excluding areas devoted to the following: rubbish rooms and custodian closets, vestibules, stairways, escalators, and elevators; areas used for electrical, telephone, computer, or mechanical equipment; loading docks and receiving areas; non- occupied areas devoted to building structure, support, or aesthetics; mall and concourse areas not occupied by retail kiosks or vendor stands; public seating areas (not including restaurant and café seating); public walkways; and public rest rooms.