The Siemens 5SU1353-1GV16 is a SENTRON 5SU1-series RCBO (residual current circuit breaker with overcurrent protection) combining a 16 A rated current C-curve MCB and a 30 mA residual current device in a single 2-module (36 mm wide) package.
The 4.5 kA breaking capacity at 230/400 V is the standard domestic and light-commercial SCCR; if your fault-current study shows more than 4.5 kA prospective short-circuit current at the installation point, you need an upstream current-limiting device or a higher-rated breaker. The 16 A rating is thermally compensated across the full ambient range: it holds 16 A at 30 °C, derates to 15.2 A at 40 °C, and steps down to 12.32 A at 70 °C — so if the RCBO lives in a hot panel (say, next to a transformer or drive), you must use the 70 °C figure for your continuous-load calculation, not the 30 °C headline.
Supply can come from either top or bottom.