I've never understood it to be literal, but from my experience there is a big difference between the folks that show up to work on time, jump right into their work, they pay attention in meetings, know code base, and have the ability "lock in" as my kids say. On the other hand you have folks that show up late, spend all day chatting at the water cooler, get distracted with home stuff, comment on hacker news all day, and only manage to squeeze in a few hours of actual work a day.