withholding tax invoice or line ??

Hi, I have setup the withholding tax at the payables options(at validation time) and supplier sites. Now when I create an invoice and provide the withholding tax pay group. Now when I validate the invoice, it is creating an additional invoice line in the same invoice. 

However the documentation and setup says it creates an additional invoice(not line). 

Is there anything missing here setup wise or do I need to run any program. Or is the invoice line only is created not invoice.

Can someone share their thoughts on this.
Thanks,Lakshmi N Jagarlapudi.