Retail uses of 5,000 sf. or less shall provide one loading space 12' x 35'. Retail uses singularly or in combination shall provide one loading space 15' x 60' for each 25,000 sf. up to 100,000 sf., plus one space for each additional 100,000 sf. up to 500,000 sf., plus one additional space for each 250,000 sf. thereafter.