The labor force is not static.
Half to 2/3 of those jobs are needed just to keep up with population growth.
Boomers not retiring at a "normal" age, and a bunch of Millenials coming out of their parents' basements and getting jobs, for example, count account for some/all of the rest.
I'm not sure I buy that completely:
July 2017 - 209,000 jobs added, unemployment rate down to 4.3%
August 2017 - 156,000 jobs added, rate up to 4.4%
September 2017 - 33,000 jobs lost, rate down to 4.2%
October 2017 - 261,000 jobs added, rate down 4.1%
November 2017 - 228,000 jobs added, rate same 4.1%
December 2017 - 148,000 jobs added, rate same 4.1%
January 2018 - 200,000 jobs added, rate same 4.1%
February 2018 - 313,000 jobs added, rate same 4.1%