The 25 kA breaking capacity per IEC 60947-2 at 440 V AC means it can safely interrupt a fault current up to 25,000 A without welding its contacts or cascading failure upstream. That's the rating that governs selectivity coordination in a distribution panel: you need this headroom to let the downstream MCB clear a fault before the upstream feeder breaker sees it.
Derating and environment — the real-world numbers
The 10 A rating holds at 35 °C ambient. At 40 °C it derates to 8.89 A; at 50 °C you're at 7.63 A; at 55 °C it's 6.91 A.
Width is 36 mm (2 MW). The combined terminal at top and bottom accepts a range of conductor sizes; the breaker ships with IP20 protection when conductors are connected, so it's safe for finger-probe access in open panels. Neutral conductor is not switched — this is a 2-pole breaker for line and switched phase only, not a 2-pole + neutral device. Supply can come from either end (line/load reversible).