The total surface area (in square feet) of non-illuminated signs on a zoning lot shall not exceed three times the street frontage of the zoning lot (in feet), and in no event shall exceed 150 square feet for interior or through lots or 150 square feet on each frontage for corner lots. Each commercial establishment shall be permitted not more than one sign. The vertical dimension of any sign shall not exceed three feet. The provisions of this Section shall not apply to projecting signs that comply with the provisions of Section 101-131 (Permitted projection).