The amortization comparison shows you how your traditional mortgage would be paid off verses how fast you can pay your home by using the software. "Principal Paid" and "Interest Paid" are running totals of how much total principal and interest paid up until the end of the calendar year. They do not reflect a yearly window but if you are interested in finding out how much principal or interest was paid in a particular year, simply subtract the total interest or principal paid from one year from the next year that appears on the chart.