And just to give a little background on why it returns a negative amount...
Assuming that scenario that you have, consider that you're applying for a loan, and the bank gives you $1000.
Now, in YOUR balance, you see a credit of +1000, correct ?
Now, the bank tells you, ok, every month you must pay 185.30.
What that means is that in YOUR balance, you'll have a debit o 185.30, correct ? that, mathematically, represents -185.30, to "compensate" for the +1000 that you received.
If you changed the formula to
=PMT(4.25%/12,60,-10000)
where -10000 represents for example, an investment (A debit in your balance), Excel would return
+185.30
, in other words, the earnings of that investment, positive, to "compensate" for the investment.
Does that help ?