It carries a 63 A rated current and a 300 mA residual tripping current, Type A, meaning it detects pulsating DC as well as sinusoidal AC fault currents — the standard for circuits with single-phase rectifiers or electronics.
Rated at 63 A continuous, with no derating needed up to 65 °C — at 65 °C it's still good for 56.96 A, and at 70 °C it holds 48.2 A. The short-circuit current rating (SCCR) is 10 kA per IEC 61008-1, and it's rated for 0.8 kA under EN 60898. The 300 mA sensitivity is typical for protection against fire risk from ground faults, not personnel shock (that's 30 mA). The supply can come from top or bottom, which simplifies panel wiring. Depth is 70 mm, so check your enclosure depth — standard shallow consumer units may be tight.