The 125 A frame at 40 °C is the continuous current you design the feeder for; it holds flat through 50 °C and only starts to taper at 55 °C (122 A), dropping to 114 A at 70 °C. That means in a warm panel — say 50 °C ambient — you still get full 125 A without derating. The interrupting ratings step down with voltage: 187 kA at 240 V, 121 kA at 415 V, 76 kA at 440 V, 17 kA at 500 V. At 480 V typical of North American industrial panels, you'd interpolate between the 440 V and 500 V figures — still well above most service-entrance fault currents. The TM220 overcurrent release means it's a fixed thermal-magnetic trip — no electronic adjustment, no communication module. That's a simpler, more rugged choice for a fixed-load feeder where you don't need to dial in the trip curve.
The case dimensions are 130 mm high, 76.2 mm wide, 70 mm deep — that's a compact 3-pole MCCB footprint.