What are the rating ranges of your recommendation levels?
It is hard to put a concrete number on our recommendations, which is why we use the more open ended labels "beginners, casual, intermediate, and advanced". However, a decent approximation may be:
Beginner: 800-1000 ELO
Casual: 1000-1400 ELO
Intermediate: 1400-1800 ELO
Advanced: 1800-2100 ELO
Expert: 2100 - 2400 ELO
It is hard to put every player in the same "box". One beginner may find use in a casual or intermediate course, whereas another beginner may be well advised to stick only to beginner courses. Similarly, some Intermediate players may feel comfortable with Advanced courses, and so on.