Acquisition debt means the original loan you took out to purchase the home.
If you purchased a home for 300,000 and put 20% down, your acquisition debt for that home loan would be 240,000.
On the date it was last secured by your home refers to the amount left on that original loan if the home was refinanced. If the original loan was 240,000 and you paid it down to 200,000 then refinanced it for 260,000 the acquisition debt for this loan is 200,000. That's how much the new loan PAID for the old loan.
The Home Acquisition Debt value calculated by TurboTax seems too low. How do I review the calculations TurboTax used to determine this value?
In a desktop version you will use the "Forms View" and look for or search for the "Home Int Wkst (lender name)".
In online versions you will need to print/download your return and select the option to print all forms/worksheets. You will then look for the "Home Int Wkst" as well.
For online versions: In the left hand menu click "Tax Tools" and then "Print Center".