What you're looking at
At 415 V and 440 V it still holds 121 kA, dropping to 75.6 kA at 500 V and 4.5 kA at 690 V, so the voltage class of your installation drives which breaking capacity number applies.
Thermal derating — what the 250 A rating really means
Above that it derates: 241 A at 55 °C, 232 A at 60 °C, 222 A at 65 °C, and 213 A at 70 °C. If your panel internal ambient runs 55 °C (common in a packed enclosure with other heat sources), you're limited to 241 A continuous — not the full 250 A. That's the heat the breaker dumps into the enclosure — factor it into your thermal budget if the panel is sealed or has limited ventilation.
Panel fit — dimensions and mounting
Depth of 86 mm means it clears most standard-depth enclosures without a sub-panel spacer.