Basically i just want to know will the machine be able to tell i put a high cost item in the bagging area that just so happens to have a cheaper barcode? Specifically if the barcode is a sticker that was made in store, like if it was a $3 piece of cheese wrapped and tagged in that store, but i scanned a $15 steak? I assume they have to be similar enough in weights. And if so how much room for a weight difference can it be? Does the barcode tell the machine the exact weight so it knows exactly how much weight should have been added to the bagging area? there has to be a little bit of wiggle room there right?

how precise is that weight calculations for the baggage area?

not worried about stuff like boxes with a upc made by the manufacturer, specifically just stuff that is both tagged in that store.