Skipped or Missing Order Number (order id)

The system allocates an order number when a customer adds an item to the cart.  This is done so that the "memo" field on the payment gateway's system will match.  If that particular transaction / order fails to process or the order is not completed,  the system will attempt to retrieve that number to avoid a gap in the sequence.  There will occasionally be times where the system is unable to recycle the number, this does not mean that you are missing an order, it simply means that the order number allocated to an order was never completed by the customer.