On May 9, I reported that under Mayor de Blasio's executive budget, the city's four library systems were set to receive major increases in their operating funds.

Figures in the new executive budget (see page 2E here) for the 2015 fiscal year, which begins July 1, suggested that the New York Public Library, Brooklyn Public Library, Queens Borough Public Library and Research Libraries all stand to get increases of more than 20 percent over what they had to spend under their modified budget for the current fiscal year.

While my math was right, my understanding of budget practices was lacking. Turns out the libraries actually had more to spend in the current year than the budget indicates because the city prepaid some of their 2013 expenses in 2014.

According to the city's Office of Management and Budget, when you factor that in, the funding to the systems is actually fairly consistent over recent years and into the budgeted future.

Sorry for the error, folks. We're correcting the stories where my un-fact was mentioned.