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 paragraph (a)(2) of Section 23-16 (Special Floor Area and Lot Coverage Provisions for Certain Areas) shall apply:

(a)        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

(b)        to the entire building where 75 percent or more of the total floor area of such building is allocated to residential use.