The idea is a simple one and much needed in todays day and age of iffy supply issues. At the moment we may raise a purchase order for 50 lines. It is unlikely that all 50 lines will be delivered in one hit. It it time consuming and open to human error to have to zero the values you are not receipting in and receipting in the correct number of items you have received. It is much less open to accidentally receipting an order in incorrectly if you are not receipting anything in in the first place. A lot of times I have accidentally receipting stock in by not zeroing the correct line. The work needed after the effect to correct it is extremely long winded.