In Subdistrict A, for zoning lots containing a building that is developed or enlarged pursuant to the applicable tower regulations of Section 98-423 (Street wall location, minimum and maximum base heights and maximum building heights), the provisions of Section 23-242 (Special tower provisions) shall apply:

1. to only the residential portion of a building where less than 75 percent of the total floor area of such building is allocated to residential use; and
2. to the entire building where 75 percent or more of the total floor area of such building is allocated to residential use.