Term of Payment is not showing in due date in Vendor Invoice

Dear Experts,

Why Term of payments is not calculating with due date, while making vendor invoice, help!

Example : As on this vendor master form "Term of Payment " is 60 days, so due date will be 60 days later. But while invoicing PO it doesn't take that 60 days of term of payment.

Thanks And Regards,

Shabir Ahmad