How does instant order work?
When you place an instant order, we add an order at the current bid or ask price (depending on the type of the order). If there is not enough bitcoins available at that price, your order will remain open until someone sells or buys additional bitcoins at that price. Our trading engine will then reposition your order every 10 minutes to the current order book offer.
May price rise after your inital buy order? Just cancel and re-enter