Record less quantity than ordered in ZOHO inventory

Record less quantity than ordered in ZOHO inventory

Lets say I ordered 100 widgets from a Vendor. I have paid the Vendor month ago and just waiting for the product to ship. I have finally received the products but have only received 80 widgets.  I see no way in ZOHO to only receive 80 widgets.  ZOHO is forcing me to receive all 100 widgets even though I have only received 80. 

How do I record that I only received 80 widgets and the vendor will send 20 widgets later?  This is a very common problem where the customer receives the wrong quantity.

I cannot find a straightforward way to do this. only a few clunky workarounds.