The Siemens 5SY4503-8CV is a miniature circuit breaker (MCB) with a D tripping characteristic, rated for 3 A, single-pole plus neutral (1P+N), and a rated ultimate short-circuit breaking capacity (Icu) of 15 kA at both 230 V and 400 V. The 1P+N configuration switches the line conductor and provides switched neutral isolation, common in single-phase final subcircuits across European-style distribution boards.
For a 3 A D-curve MCB, that's a generous breaking capacity; it gives headroom over typical domestic or light-commercial prospective fault levels.