In reviewing the cash receipts journal, Andy discovers that a piece of furniture purchased on 6/30/2014 for $25,000 being depreciated using the straight-line method with an estimated salvage value of $5,000 and a useful life of 5 years, was sold on March 31, 2017 for $6,000 cash. Unfamiliar with the proper accounting, the bookkeeper debited cash and credit sales for the receipt of the $6,000. What is the adjustment?