Posted Purchase Receipt GRN Report

On purchase line initially my inputs are:

OrdQty is 100, QtytoRcv of 80 and automatically Qtyto invoice will take values from QtytoRcv.

After posting by receiving the items, I get the below report frm posted purchase receipt.  Leaving out a short fall of 20 items. 

However hours later my vendor delivered the remaining items of 20. 

Then: on the same purchase order my imputes are:

OrdQty = 100, QtytoRcv = 20 the same way Qtytoinvoice will take values from QtytoRcv.

After posting again by receiving the items, I get the below report frm posted purchase receipt.  Leaving out a short fall of 80 items instead I should be having a short fall of 0. Showing no outstanding order quantity.

Please can help me out technically?

Thanks