Retrospective change of flat rates by RERA definition of carpet area

For an ongoing project by any developer, if the flat has been bought based on super built-up area and the agreement had also been signed accordingly back in the year 2011. Is the builder liable to make adjustments to the final installment to be paid for possession as a result of the decrease in salable Carpet Area with respect to sold Super-Build Up area? 950sq.ft.- Super Built-up area 893sq.ft.- Carpet Area (including internal walls) Am I eligible for a return of the amount paid or adjustment of the amount due in the final installment against the decrease of 57sq.ft? If yes, should I challenge this before paying up the final installment with the builder/developer itself or should I do so after via consumer court?