Your calculation is wrong.
Put in zeros for each month that you didn't have the loan in 2020.
Do this for each loan and calculate the average principle balance.
For example, if the loan is for 1.2 Million but you only have it for December. Divide it by 12 and the average principle is 0.12M or 120K. Do this for each loan.
Details: Jan through November is 11 zeros. December is 1.2 Million. So the average is 1.2M/12.
Now, you can add them. Enter that for the outstanding principle.
