Luke 16:5

Called every one. Or, “summoning his master’s debtors one by one” (RSV). The steward carried out his scheme systematically and diligently. Had he used the same diligence and skill in furthering his master’s interests that he used in furthering his own he would have been a success rather than a failure. As a servant in the house of Potiphar, Joseph exhibited those traits of character that endeared him to his master (see Gen. 39:1-6). By promoting his master’s interests as if they were his own, Joseph found himself promoted to be steward over Potiphar’s household.

How much owest thou? It would almost seem that because of incompetence or neglect the steward had either incomplete records or no records at all of previous transactions. If so, he could connive easily with those who purchased his master’s goods to defraud the master and to benefit both himself and the purchasers at the master’s expense.