In the case of an interior lot, no fence panel, picket or slat shall be erected in the required front yard in excess of three feet in height. On a corner lot, no fence panel, picket or slat in excess of three feet in height shall be erected within the required front yard setback of all street lines. The total height of the top of the fence panel, picket or slat shall not include any slight undulations of the ground. An allowance of six inches from the bottom or any fence panel, picket or slat is permitted, provided that 80% of the fencing does not exceed a height of three feet two inches above the ground. This maximum height is intended to allow a three-foot-tall fence panel to be installed up to two inches above the ground, regardless of any undulations of the ground up to six inches above the ground when the ground does undulate. No fence post, including any decorative finial, shall be in excess of three feet six inches.