Recalculated Scheduled Payment Issue

1) User has created One Invoice in AP on 12-JAN-2012 with Invoice date 16-DEC-2011 and Payment Terms given as NET 30 in Header Level and after that he didn't touched that invoice

 

2) Yesterday he matched the above invoice with PO and validated and accounted

 

3) When he goes to the schedule payment tab payment Due Date it is showing as 02-MAR-2012...

 

4) Invoice DAte is 16-DEC-2011 and payment terms are NET30 and due date should be 27-JAN-2012(This is the issue)

 

I have checked the setup's in Payables Option

 

In Invoice Tab

 

Recalculated Scheduled Payment check box got enabled and i think that's the reason system has recalculated the Payment Terms it seem's