Does this "fewer days of work" refer to "multiple days' of work" or what?
f1)Did you know that a bright room can make you happier and more hard-working? A recent study suggests that students do better on tests in sunny schools...In offices, workers who have windows near their desks work harder than those who don't. They also miss fewer days of work.
No, it refers to the amount of days missed by a worker over a period of time, say a year. Compared to those workers who don't have windows.