At 415 V and 440 V it still holds 242 kA, and at 690 V it drops to 17 kA. For a 480 V delta panel, the relevant figure is the 242 kA at 440 V, which covers most industrial service-entrance requirements. The TM220 overcurrent release provides thermal-magnetic protection: the thermal element handles overloads up to the 320 A frame, and the magnetic element responds to short-circuit currents.
Rated current holds at 320 A from 40 °C through 50 °C (–), then derates linearly to 292 A at 70 °C. The 80.1 W maximum power loss should be factored into enclosure thermal calculations, especially in a sealed panel.