Change:
//START HOW MANY ORDERS
define('ENTRY_CUSTOMER_ORDERS', 'Previous Orders:');
define('ENTRY_CUSTOMER_ORDERS1', '0');
//END HOW MANY ORDERS

//START HOW MANY ORDERS
define('ENTRY_CUSTOMER_ORDERS', 'Previous Orders:');
define('ENTRY_CUSTOMER_ORDERS1', '1);
//END HOW MANY ORDERS

Need to change 0 to 1 or customers with 1 order are shown as 0

More...