FBI admits it grossly misstated encrypted device numbers

We have previously reported on the GrayKey device, which is spreading through law enforcement agencies across the country. This of course was in tandem with various reports detailing law enforcement's constant frustration regarding encrypted devices. To this end, the Federal Bureau of Investigation has spearheaded the call for tech companies to create back doors and to develop technology that will allow them to access any locked device. A centerpiece of this battle has been the number of devices the Bureau and other agencies claim they have been unable to access and they often cite this as a major obstacle to their ability to solve a crime or prevent terrorism. The FBI alone claimed they were blocked from accessing over 7,800 devices in just one year. This figure was touted in various places, including the Congress of the United States.
So how true was it?
source: Washington Post