Box 51 is dividend credit. The US does not have a dividend credit and ordinary dividends are basically taxable dividends.
Lines 51 and 52 – For those credits, addback of credits, and recaptures that are not specifically listed on Form IT-204-IP, the partnership provides you with the code and your distributive share of these items. You must complete a separate credit form reporting your distributive share of the credit, credit components, credit factors, and recapture of credit for each credit listed. See the credit chart for a list of the codes for the credits and add backs entered on lines 51 and 52.
NY IT-204-IP-i