The Siemens 5SM3646-0 is a 4-pole SENTRON residual-current circuit breaker (RCCB) rated for 63 A at 45 °C and 400 V AC, 50 Hz, with a 300 mA AC-type trip and a 10 kA short-circuit current rating. That 300 mA sensitivity is for general fault protection on a 4-wire system — not the 30 mA you'd spec for personal shock protection on a branch circuit.
The supply can come from top or bottom, which is handy when you're retrofitting into an existing distribution board where the busbar is already landed.
The thermal derating curve is published: holds 63 A up to 45 °C, then drops to 60.48 A at 50 °C, 57.96 A at 55 °C, 55.44 A at 60 °C, 52.92 A at 65 °C, and 50.4 A at 70 °C.