Parkview- plot location change- urgent advice

I need an advice from the experts please.
I booked a plot 50x90 proper corner in parkview islamabad in 2018. In their revised map my plot dimensions are very irregular. Although it has 6 marla extra land with it but dimensions are 90x99x18x120 instead of proper 90x50.

Their engineer told me that as per cda bylaws you have to leave open 15 feet in the front, 10 feet at the back and 5 feet on each side. So as per this calculation he said that, maximum covered area on the ground floor can be 2700.

He told me that even in my irregular dimensions i can make either 60x60= 3600 or 64x50=3200.

Is it true.
I would really appreciate your advice whether i just accept this or insist to give me an alternative plot