What the ratings mean for your panel
The 5SU9304-0KK25: The 25 A rating at 30 °C tells you the continuous current it'll carry in a typical 30 °C panel environment. That derates to 23.5 A at 40 °C and 21.75 A at 50 °C — so if your enclosure runs hot, you need to account for that drop. The B-curve means it trips at 3–5 times rated current, which is standard for residential or light commercial lighting and socket circuits where inrush isn't a concern. The 10 kA breaking capacity is the fault current it can safely interrupt — adequate for most sub-distribution boards downstream of a larger main breaker. It's a 1P+N RCBO, meaning it switches the live pole and protects against overcurrent and residual current (AC type,) on that pole, while the neutral is switched but not protected. The 18 mm width takes up one modular space on the DIN rail, so you can pack it tight in a distribution board. It accepts solid or stranded conductors from 0.75 to 35 mm², which covers everything from lighting circuits to small sub-mains.
Where it fits in the system
Mounts on a standard DIN rail in any position — top or bottom feed. The installation depth is 70 mm, so it'll sit flush in a typical distribution board. IP20 with conductors connected means it's for enclosed panels only, not washdown or outdoor duty. Ambient temperature range is -25 to +45 °C, which covers most indoor industrial and commercial environments.