Every area statement you will be handed in Siliguri uses the same four ideas, and confusing them is the single most common reason buyers feel short-changed at handover.
Carpet area is the usable floor inside the walls of your flat. Built-up area adds the thickness of the walls and, in most schedules, the balcony. Proportionate common area is your share of lobbies, staircases and corridors. Super built-up area is what you are usually quoted a rate against.
At The Crest the calculation is printed on the drawings: super built-up area equals built-up area plus proportionate common area, plus 20 per cent. On the commercial side the formula is built-up area plus the passage in front, plus 20 per cent.
Ask for the schedule that shows all four columns for your specific unit number, and match it against the sanctioned floor plan before you sign anything.