Newly placed orders first enter the order book as an "open order" in sequence of their timing placed. When some of your "open order" matches with another order, it becomes a "partially matched order". When all your order matches with another user's order, it becomes a "fully matched order" or "completed order". Completed orders are removed from the order book. Open orders can still be canceled if there is any pending quantity that is open to cancel. 

You may sometimes face a challenge in canceling an order if it has already been matched by our platform but the status update is still in progress.