Occupant load is calculated based on use of the space (not occupancy classification).
For example, a meeting room for fewer than 50 people in an office building is not an assembly occupancy; it is a business occupancy, but its occupant load is based on an assembly use.
The same concept applies to a classroom in a university, which, although classified as a business occupancy, would have its occupant load based on educational use (for traditional classroom style) or assembly use (for lecture style).