Error in Quantity to receive NAV

Hello
I have a problem while i try to modify with a function added in Functions in Purchase order. I should modify the specific values of quantity and quantity invoice, to invoic ,received and to receive. The only wrong value is Quantity to receive .I cant understand why it updates with a value it should not when the conditions are always the same as for the other values. Anything i should check before update it ????????

Thank you in advance