Please not that the F&O ban is not about long or short positions. It only says that you can initiate fresh positions but you can close existing positions in F&O. That means if your long on a F&O ban stocks you can sell and close the position or reduce the position. Similarly, if you have a short position, you can buy the future and close or reduce the short position. You cannot fresh positions or add to your existing positions. This applies when the open interest of the stock crosses 90% of the market wide position limits (MWPL).