When located in the "C-3", "M-1" or "M-2" Districts, one (1) space for twenty thousand (20,000) to fifty thousand (50,000) square feet of gross floor area; two (2) spaces for fifty thousand (50,000) to two hundred thousand (200,000) square feet of gross floor area; one (1) additional space for each seventy-five thousand (75,000) square feet of gross floor area in excess of two hundred thousand (200,000) square feet.