I think it's an honest and realistic question for them to provide more than a canned response or to quote specs that mean nothing in and of themselves unless you look them all up.
Ask them how that type of an error can occur, as in what are the circumstances under which a mis-reading like that comes about. These are just examples but at least it will give them something to answer to: Improper handling of the sample, not using enough sample or not making sure it was mixed and not separated out, contamination of the sample by another sample they were working on at the same time, improper heating of the sample.