Entering Mortgage Payments as Special Expenditure

I am attempting to enter house mortgage payments using the Special Expenditure folder rather than the Primary Home folder (I'm tinkering with different accelerated payment options). I already know to select "Not Tax Related" for the principal portion of each payment and "Tax Deductible" for the interest portion of each payment. But is it correct to enter each payment IN DOLLARS (rather than selecting IN TODAY'S DOLLARS) so that I get the same declining value of these payments to show up in the Special column of the Total Spending report (similar to what I would see for mortgage payments in the Housing column)?

I'm a little confused because my simple test using a fixed mortgage ($50,000 over 5 years at 6.25%) yields slightly different results when I enter this as a mortgage payment in the Primary Home folder ($11,324 today's dollars in year 1, $10,994 in year 2, $10,674 in year 3, $10,363 in year 4 and $10,061 in year 5) than when I enter the payments in the Special folder ($11,670 in year 1, $11,329 in year 2, $10,999 in year 3, $10,679 in year 4, and $10,369 in year 5). Interestingly, the payment comparisons seem to be off by 1 year (e.g., the year 1 payment of $11,324 in the housing column almost matches the year 2 payment of $11,329 in the Special column, and so on).

I'm sure I'm missing something very basic here.

Rick