I was curious too, so I took a closer look. The beginner/"pupil" curriculum is 28 "days", or 448 study-hours. Conveniently for comparison, a college course is

I was curious too, so I took a closer look. The beginner/"pupil" curriculum is 28 "days", or 448 study-hours. Conveniently for comparison, a college course is generally 15-16 weeks long. A 4-credit course would be 4×16 hours classroom hours, so a 4-credit course with 3 study hours per classroom hour would be 12×16 hours. So the beginner curriculum is equivalent to two and a half of the hardest 4-credit courses in your degree program. The intermediate/"specialist" curriculum is 37 "days". I would imagine the "acm day" is both to not scare away the potential student and to actually make designing curricula of that magnitude feasible. (I used to write K-12 curricula professionally, and it's no small task.)