It's a line-protection device — meaning it protects cables and busbars from overload and short-circuit, not motor or generator circuits. The 250 A rating holds flat from 40 °C up to 50 °C; above that it derates to 241 A at 55 °C, 232 A at 60 °C, 222 A at 65 °C, and 213 A at 70 °C, so if your panel ambient runs warm, factor the actual load against the derated figure, not the nameplate 250 A. At 240 V it interrupts 187 kA; at 415 V and 440 V it's 121 kA; at 500 V it drops to 79 kA; at 690 V it's 5.1 kA.
That 140 mm width on a 4-pole frame is standard for this class — it occupies four 35 mm DIN-rail modules (roughly 35 mm per pole). It comes with 3 auxiliary switches (HQ type) pre-installed, so you have remote status feedback without adding a separate accessory block. The ETU320 trip unit is a basic electronic release.