Do you think this is a clear instruction?
"That's because students can book classes until 24 hours before class starts."

In the system, students cannot book a class within 24 hours before the class starts, in this case, do you think the instruction is precisely expressed?

Question

Do you think this is a clear instruction?
"That's because students can book classes until 24 hours before class starts."

In the system, students cannot book a class within 24 hours before the class starts, in this case, do you think the instruction is precisely expressed?

Answer

Say "up until" instead of "until" 
besides that its perfect!