Scale on Map—Determination by Commission. Where property is indicated on the zoning map as acreage and not subdivided into lots and blocks, or where the zone boundary lines are not approximately street, alley or lot lines, the zone boundary lines on said zoning map shall be determined by scale contained on such map and where uncertainty exists, the zone boundary line shall be determined by the planning commission. In the event property shown as acreage on the zoning map has been or is subsequently subdivided into lots or blocks by a duly recorded subdivision map and the lot and block arrangement does not conform to that anticipated when the zone boundaries were established, or property is resubdivided by a duly recorded subdivision map into a different arrangement of lots and blocks than shown on the zoning map, the planning commission, after notice to the owners of the property affected thereby, may interpret the map and make minor readjustments in the zone boundaries in such a way as to carry out the intent and purpose of these regulations and conform to the street, block and lot layout on the ground. Such interpretation shall be by written decision, and thereafter the zoning map shall be changed to conform thereto.