Amortization of Mortgage Loan Fees for Rental Property

My accountant was inaccurately amortizing my mortgage origination fees over 30 years for my rental property.  I have a 15-year mortgage.  Thus, the amount amortized to date is very low.  However, when I change the "years to fully depreciate" to 15 years, the "estimated expense" for 2021 is such a small amount that it would take over 10 years to fully amortize.  I only have a couple more years before I reach the 15-year mark.  How can I override this so that I am getting the appropriate $ amount of annual amortization?