The NEC has two sets of rules for the minimum size of feeder conductors. There’s one set for feeders not over 600V [215.2(A)] and another for those over 600V [215.2(B)]. Each subsection is broken into three sub subsections.
NEC: Feeder Conductors, Part 2
At first glance, it seems (A) and (B) don’t correspond with each other. But look closer, and you’ll see some harmonization.