Since you can't "lose" educational status once you get into that top bucket, that of a Bachelor's or better, the only way out of that bucket is to die.
The 316k drop number referenced is from the Civilian labor force.
Civilian labor force, or labor force
The labor force includes all people age 16 and older who are classified as either employed and unemployed, as defined below. Conceptually, the labor force level is the number of people who are either working or actively looking for work.
The 316k drop number referenced is from the Civilian labor force.
https://www.bls.gov/cps/definitions.htm#laborforce