Addition Of 50% Terrace Area In Flat Carpet Area

I've a flat in Seawood, Navi Mumbai which has carpet area of 60.38 Sq. mtr and 2.42 carpet area of terrace clearly mentioned in Sales Deed. Now Cidco has given me NOC payment note slab falling between 61-70 claiming to add 50% of terrace area in original carpet area of 60.38 sq.mt. otherwise I would have fallen into slab of 51-60 and would have save lots of money. Need to know the ruling of adding 50% of terrace carpet area in original flat area.