It protects a single-phase final subcircuit against both overload/short-circuit (via the C-curve magnetic-thermal trip) and earth leakage (Type AC, 30 mA residual sensitivity implied by the class). The 40 A rating at 30 °C ambient means it can carry a continuous load of that magnitude; the derating curve drops to 37.6 A at 40 °C and 29.2 A at 70 °C, so the actual continuous current in a warm enclosure is lower than the headline number — a common trap when populating a crowded panel.
The higher 15 kA rating gives headroom for coordination with upstream fuses or MCCBs in an industrial panel — a detail that matters when the site electrical engineer is checking selectivity tables.
The installation depth is 70 mm, with an overall depth of 77 mm including the front face. The IP20 rating is conditional on the distribution board being installed and conductors connected; it is not a standalone ingress-protection figure for open-panel use.