There's no real way a turker would know if the data is bad. Really only the merchandiser at HQ who was checking with the supplier would have had the source data (dimensions, units for those dimensions, case quantities, and so on) or warehouse workers who actually receive the product and can physically look at it. Suppliers sometimes change product attributes, quantity per case or pallet, or packaging without giving advance notice so the warehouse often ends up making these updates as they notice them, if they do. Data quality in supply chains is a constant struggle for many companies. It sounds like Target got hit bad with this due to a perfect storm of poorly trained merchandisers and SAP having dummy data that probably looked somewhat reasonable to the untrained eye.