The floor area modifications of this Section shall apply as follows:

(a)        Floor area exemption

The floor space contained within any easement volume shall be excluded from the definition of floor area.

(b)        Commercial floor area in Residence Districts

Where special use allowances pursuant to paragraph (a) of Section 66-222 (Special use allowances around easement volumes) are permitted in Residence Districts, the maximum permitted commercial floor area shall be equivalent to the area permitted for commercial uses pursuant to such Section.