What this RCBO does on the rail
The Siemens 5SU9356-7KN63 is a 2-pole RCD-operated circuit breaker (RCBO) from the SENTRON family, combining overcurrent protection and residual current detection in a single 2-module-width (36 mm) package.
Derating and ambient — the real-world current
At 40 °C it's 59.22 A, at 45 °C it's 57.33 A, at 50 °C it's 54.81 A, and at 55 °C it's 51.03 A. If the distribution board runs warm — say, a packed enclosure near a drive cabinet — use the 40 °C figure for your continuous load calculation.