The bulk regulations of the underlying districts shall apply except as modified by the provisions of this Section, inclusive. For the purposes of applying the provisions of this Section, inclusive, the bulk regulations for residential portions of buildings in Commercial Districts are modified as follows:

1. In C4-3 Districts, the applicable residential equivalent shall be  an R6-1 District, as modified by the provisions of this Section, inclusive, shall apply; and
2. In C4-4 Districts within Subdistrict B, the applicable residential equivalent shall be an R7-3 District, without a letter suffix, shall apply.