It looks best if you have an even number of scarves hanging from the window. So 2 or 4 or 6 etc., because then you will have the same amount of fabric hanging to the left and right of the window when the curtain is open. To cover a width of 280 cm and get beautiful, even waves, you should use about 540-560 cm of fabric (= 280 cm x 2 with a border of about 20 cm). Now divide this 540 cm by the number of curtains you want and you have the width of the curtain. For 2 curtains this would be approx. 270 cm per curtain (= 540 cm / 2) and for 4 curtains approx. 135 cm per curtain (= 540 cm / 4).