"…we discovered inconsistencies in EQUIPMENT VALUATION to Ukraine."
"used REPLACEMENT COST instead of NET BOOK VALUE."
Net book value (NBV) would be a much much lower value of the equipment. So, NBV would be the original cost of the equipment, whatever the price tag was per contract, less annual DEPRECIATION of the equipment. Annual depreciation is only a book entry, meaning no actual $$ dollars exchange hands. It is an accounting method that helps to show the equipment on the books at a value that more closely resembles the actual current value of the equipment due to wear and tear or age of the equipment. The REPLACEMENT COST would be the current market value if that equipment were purchased with today's dollars. You NEVER would EVER use REPLACEMENT COST on your balance sheet as that would be VERY MISLEADING!!! REPLACEMENT COST would only be used or presented in the Notes to the Financial statements or for Insurance reporting reasons.
So this $6.2 BILLION dollar accounting error is a mere book entry. No actual money was found!!