It means the property on this corner is zoned in a way that allows mid rise residential with commercial first floor by right. The other three corners are zoned CMX4, which can be quite a bit taller, like 11 stories by right with bonuses, or 22 stories with half lot coverage. Or so. My point is clarke SUCKS because he's responsible for this disparity, and furthermore he's responsible why this mega corner with subway stops /trolley stops and wide streets on both sides isn't all CMX5(skyscraper zoning) by right, as broad street should be from Oregon to the boulevard

Hence:

MANDATORY SKYSCRAPERS