The R-1-7 zone classification and the minimum dimensions requirement prescribed for said classification shall be considered to be the basic or standard lot size throughout the City; provided, however, that in those areas placed in the R-1-7 classification, if a subdivision map is filed, the minimum lot sizes for 20 percent of the lots created by said subdivision may be reduced to 6,000 square feet, and 10 percent of the lots thus created may be reduced to 5,000 square feet, said lots being subject to those minimum dimensional requirements as set forth hereinabove for such lot areas; provided, that the average lot size of all the lots within the subdivision shall equal a minimum of 7,000 square feet. (Ord. 3153 § 2 (Exh. A), 2010; Ord. 1500 § 2, 1973; Ord. 1212 § 1, 1969; prior code § 33.503(H)(1)).