The C63N3TM630 is a 3-pole ComPacT NSX630N circuit breaker rated 600 A at 40 °C with a TM-D thermal-magnetic trip unit. The 85 kA Icu at 240 V AC is the maximum short-circuit current it can safely interrupt — at 415 V AC that figure drops to 50 kA Icu, which is the rating code N (50 kA at 415 V AC). For distribution panels fed from a transformer of that size, this breaker gives you the interrupting capacity to clear a bolted fault without upstream devices having to trip. The TM-D trip unit provides L (thermal) protection for overloads and I (magnetic) protection for short circuits. No earth-leakage protection is integrated — if you need that, it goes external or you step to a Micrologic electronic trip.
Overvoltage category III suits fixed-installation distribution boards.