Read a different way "Last night there were at least 400 people eating dinner at 8:00PM" means that there were at least 400 people who either don't have families or for whatever reason felt it was better to stay at the office than to be at home w/ their families. The novelty of eating in a company cafeteria wears off, the long-term grind of working for a company where there is pressure to put the company ahead of your personal life does not.