The district boundary lines shall be as shown on the Zoning Map. Figures indicating number of feet appearing on said map between a road, street, avenue or railroad right-of-way and the boundary line of a district mean that the boundary line of the district at such location runs parallel with the street line of the road, street, avenue or railroad right-of-way at the distance therefrom indicated by the number of feet marked. Where said map indicates a district boundary approximately in a street, the center line of such street shall be construed to be the boundary. In each case of doubt or disagreement concerning the exact location of the boundary line, the determination of the Planning Board shall prevail.