Editing the order during checkout
To change the items in the order during checkout, customers must reopen the shopping cart. To open the shopping cart from the checkout process, customers can click the # Total Products, # Total Quantity link in the Order Summary section of the checkout. On your website, the # character is replaced by the number of unique items and the total number of items in the order. When customers click the order summary link in any checkout step except the Confirmation step, they can then click the Edit Shopping Cart link to update the items in the order.
Customers can use the Order Summary section to review their orders during the Confirmation step of the checkout process, but they cannot change the order during confirmation.