Delay in possession and not paying adequate compensation

I had booked a flat in Greater Noida in 2011 and was supposed to get possession by Jan 2014. As per their own admission, the builder agreed that they are already late and might give possession by February 2016. However, it was only in dec 2014, that they sent a letter stating that they have increased the floor size by 13% of the agreed size for which however they will charge only 10%. As per the agreement, they are to take consent of the flat owners if they plan to increase size beyond 10% (13% in this case) which the builder did not do. Although they are charging only 10%, they have made it clear that I will have to pay for the 13% increase during registration which of course is a monetary loss to me. Is this situation not against the agreement? Also, for two years delay, they are offering a compensation of Rs 33, 142.50 only, which as per my understanding is way less. A few others who tried to point this anomaly out were simply asked to withdraw from the plan and their money would be refunded but I don't want to do that at such a belated stage and spoil my investments. Please do advice as the entire situation is causing a loss of almost Rs 4lacs to me.