Are you using PMV?
The Help from microsoft is shown below

You can change NPV to be the number of payment.  If the payments are monthly
than 30 years would be 360 and 34 years would be 408

PMT(rate,nper,pv,fv,type)

For a more complete description of the arguments in PMT, see the PV function.

Rate   is the interest rate for the loan.

Nper   is the total number of payments for the loan.

Pv   is the present value, or the total amount that a series of future
payments is worth now; also known as the principal.

Fv   is the future value, or a cash balance you want to attain after the
last payment is made. If fv is omitted, it is assumed to be 0 (zero), that
is, the future value of a loan is 0.

Type   is the number 0 (zero) or 1 and indicates when payments are due.

What amortization schedule are you using?

If it's properly designed, you should just be able to drag the last row down for
another 4 years.