@Rainflurry , thank you!

When you say "If you want to put those 25 posters into inventory, you can enter a bill for 25 more at $0.00.", 

This bill I am entering,  is that another sales bill from the vendor of the posters?  ( Like the way I am entering the  vendor bill for the 9 posters @ $0.00/ea and dating it prior to 12-9 so that I can complete the invoice of 15 posters to and receive the payment. )?  

 I just enter another different bill that same way?  Is that correct?

Thanks again!