Greater Noida's super area math is confusing

Since last month, Whitney Build Home ka brochure dekh raha hoon Sector 81 mein. Super area aur carpet area ka difference bahut zyada lag raha. Samajh nahi aa raha yeh normal hai ya builder ka trick hai. Later on maintenance aur property tax par kitna impact hota hai iska? Investor ke liye, is it worth paying for so much common space?