Yes, I’d think it would be complicated. Full time faculty might be in the classroom maybe nine hours a week, but they are expected to keep office hours, and they are expected to do research, writing, course preparation, and so forth. So it would probably add up to a 40 hour week in practice.
Adjunct faculty are not considered full-time workers, so you would probably only count classroom hours and required office hours. In most cases that would come to fewer than 30 hours a week, although probably some junior colleges work them harder than that. But you’d need to establish whether, for instance, they should get paid for class preparation, and if so, how long that would be.
Research would not count. If they were writing articles or a book, it would be in hopes of getting a tenured position in the future—which would be full time.
Oh. And you would likely need to establish some estimate of hours needed to grade papers, exams, etc.