Loan P&I less than what it should be on tape

[Michael Roberts]

I'm looking at a 1st lien non-performing note in which the original loan amount was $117,850. The original and current rate is 4% and loan term is 360 months. The current (and original) P&I is $474. By my calculations the P&I should be $559. Wondering why the P&I would be considerably lower, something to do with the way it's amortized?