According to published reports, the deal includes Ratner getting a subsidy for 15 years instead of 25 years as per the 421-a subsidy on 1,930 market-rate condos slated for the Atlantic Yards project.
Oddly enough, the print version of the article, like the New York Times's coverage, omits the special tax break for Forest City Ratner that would remain, worth $150-$200 million. An article in the Park Slope Courier states:
Under the new legislation, FCRC buildings in the project must meet the new affordability requirements in order to qualify for a 25-year tax abatement.
Unmentioned is the 15-year subsidy available to no other developer.
The Courier-Life article states at one point:
[Assemblyman Vito] Lopez said he has met with the city six or seven times and the key issue has always been Average Median Income (AMI) guidelines as set by the federal government, which includes the metropolitan area surrounding the city.
AMI means "Area Median Income," not "Average Median Income."