The Siemens 5SL3363-7 is a SENTRON 3-pole miniature circuit breaker rated 63 A at 30 °C with a C tripping characteristic (5–10× In magnetic trip), breaking 4.5 kA per IEC 60898 and IEC 60947-2 at 400 V AC. The C-curve is the standard choice for motor-starter and transformer primary protection where inrush is moderate; for purely resistive loads a B-curve would trip faster on fault, but C is what the spec calls out here. Temperature derating is baked in: at 40 °C ambient the continuous rating drops to 59.18 A, at 45 °C to 57.96 A, and at 55 °C to 52.93 A. The 10 000 mechanical switching cycles typical service life is adequate for a distribution board seeing a few operations per year; for frequent switching duty (daily or weekly) you'd want a contactor ahead of it. Mounting position is any, which simplifies panel layout — no restriction on horizontal or inverted installation.
Snap-on DIN rail mounting, any position. The 3-module width (54 mm) matches the standard modular grid; plan for the derated current at the panel's expected ambient temperature, not the 30 °C nameplate. The sealable feature accepts a standard padlock hasp for lockout.