When uncertainty exists with respect to the boundaries of the various districts shown on the Zoning Map, the following rules shall apply:
A. District boundary lines are either the center lines of railroads, highways, streets, alleys or easements or the boundary lines of sections, quarter sections, divisions of sections tracts or lots, or such lines extended or otherwise indicated.
B. In areas not subdivided into lots and blocks, wherever a district is indicated as a strip adjacent to and paralleling a street or highway, the depth of such strips shall be in accordance with the dimensions shown on the maps measured at right angles from the center line of the street or highway, and the length of frontage shall be in accordance with dimension shown on the maps from section, quarter sections or division lines, or center lines of streets, highways or railroad rights of way unless otherwise indicated.
C. Where a lot held in one ownership and of record on the effective date hereof 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 less restricted frontage of the lot by more than twenty five feet (25').