On Jan 15, 2003 after the 12th payment is made the balance is $123,196.42

If on Jan 15th 2003 the borrower made a total payment of $680.49 + $123,196.42 that payment would be called the balloon payment and the loan would be paid in full. This is sometimes called a balloon loan.

A simple way to show this balloon payment, especially for clients, is to place the cursor on the payment cell on line 12 of the spreadsheet and change the payment of $680.49 to something in excess of the current balance ($123,196.42) say, $300,000 and press [Enter]. The schedule will then show the 12th payment as the balloon payment.