Wherever any uncertainty exists as to the boundary of any use district as shown on the zoning map, incorporated herein, the following rules shall apply:
A. Where district boundary lines are indicated as following streets, alleys or similar rights-of-way, they shall be construed as following the centerlines thereof.
B. Where district boundary lines are indicated as approximately following lot lines, such lot lines shall be construed to be such boundaries.
C. Where a lot held in one (1) ownership and of record at the effective date of these standards is divided by a district boundary line, the entire lot shall be construed to be within the less restricted district; provided, that this construction shall not apply if it increases the area of the less restricted portion of the lot by more than twenty percent (20%). (1979 Code § 5-2-4)