Density. Each lot or parcel of land in Zone C-O shall have not less than 3,000 square feet per dwelling unit, except as herein provided. The number of permitted units shall be equal to the quotient, rounded off to the nearest whole integer, resulting from dividing the number of square feet of the lot by 3,000. Quotients ending exactly in five-tenths (0.5) shall be rounded off to the next higher whole integer.