The Siemens 5SY4325-8CV is a 3-pole miniature circuit breaker (MCB) from the 5SY4 series, rated D-curve 25 A with a breaking capacity of 15 kA at 400 V AC.
The 25 A thermal rating handles continuous resistive or motor full-load current up to that value. If your available fault current exceeds 15 kA, you need a higher-rated device or a current-limiting upstream breaker.