yes, I fully agree that the right number of drums has to be visible on the bill of lading.
But if your users found a smart way and everything is fine, then I wonder why you are looking for a change.
I f I understand correct then you want 20 in pick quantity instead of 19.5
so you have 19.5 =20
and you have 20 = 20
then, how can the people know if they shall pick the 19.5 or the 20, if both just shows 20 on the pick list?
Do they really search for a small drum if they see 19.5, or do they just smile because of this stupid SAP system and pick 20 drums as usual?