(15)   Seating Space.
A seating space in a place of public assembly shall be considered as a fixed permanent seat. In the case of bleachers, benches or the flat tops of walls, seating shall be 18 in. wide and 16 in. deep. Seating 30 in. or more in depth shall count double when access is provided to both sides. In the case of open floor area used for temporary seating purposes, seating area is calculated as one seat per nine sq. ft. of open floor area.