This article is terrible, but there are much better sources:
https://www.reuters.com/article/us-usa-audit-army/u-s-army-f...
https://www.forbes.com/sites/kotlikoff/2017/12/08/has-our-go...
"The Defense Department’s Inspector General, in a June report, said the Army made $2.8 trillion in wrongful adjustments to accounting entries in one quarter alone in 2015, and $6.5 trillion for the year. Yet the Army lacked receipts and invoices to support those numbers or simply made them up."
The total of 21 trillion includes "adjustments" made by the U.S. Department of Housing and Urban Development in addition to branches of the Pentagon.