The subdivider may elect to submit a final map for all or part of the approved tentative map in the sequence of units approved by the Planning Commission. Each final map which constitutes a part, or unit, of the approved tentative map shall have a separate subdivision number. The subdivision improvement agreement to be executed by the subdivider shall provide for the construction of such improvements as may be required to constitute a logical and orderly development of the whole subdivision by units. (Ord. 5793-NS § 2 (part), 1987)