The Siemens 5SU1353-0KV40 is a combined residual-current and miniature circuit breaker (RCBO / FI/LS protector) that packs an RCD and an MCB into a single 1+N-pole module. It is listed as Type AC (wave shape) with a rated residual operating current IΔn of 30 mA and a short-circuit breaking capacity of 4.5 kA. The B-curve trip characteristic at 40 A means it handles general-purpose resistive and light inductive loads in a distribution board — the magnetic trip kicks in between 3 and 5 times rated current, so it clears fast on a hard fault without nuisance-tripping on motor inrush.
The 4.5 kA short-circuit capacity is adequate for domestic and light commercial sub-distribution where the prospective fault current at the board is below that level; for industrial panels with higher fault levels, a device with a higher Icn (e.g., 6 kA or 10 kA) would be specified.