The total sign area means the measurement of the smallest square, circle, rectangle, or combination thereof which will encompass the entire sign face. If a sign has two or more faces, the area of all faces shall be included in determining the total area of the sign, except that if two sign faces are placed back to back and are at no point more than 30 inches from one another, the area of the sign shall be taken as the area of one face if the two faces are of equal area, or as the area of the larger face if the two faces are of unequal area.