On Block 1 or 2, as indicated on the District Plan in Appendix A of this Chapter, the maximum height of a building or other structure shall not exceed 275 feet above curb level, except that the maximum building heights may be increased by 15 percent, provided that the gross area of any such story located above the maximum building height does not exceed 90 percent of the gross area of that story directly below the highest 15 percent of the building.

The underlying allowances for permitted obstructions above such maximum height limit shall apply.