Number of Signs. Each commercial use shall be entitled to one wall-mounted, canopy, or awning sign, except that where a building has street frontage on more than one (1) street, one (1) additional sign may be permitted. Any permitted use within a building having an exterior wall facing an off-street parking area may have a second principal sign on said wall if that wall contains a pedestrian entrance to said permitted use. In the event that a building has frontage on two (2) streets and a rear entrance, three (3) signs shall be permitted, however, the size of the 3rd sign is limited to fifty (50%) percent of the size of the largest sign.