The 4-pole 3P+N design switches the neutral conductor, so it's ready for TN or TT systems where neutral isolation is required.
The D curve (10–20× In) is the key selection parameter here: it's sized for loads with high inrush, typically motor starters, transformers, or discharge lighting. At 20 A, expect this to hold a 15 A motor full-load current without nuisance tripping during start-up. The thermal derating table is worth noting: at 40 °C ambient the continuous rating drops to 18.8 A, and at 50 °C to 17.52 A; if the panel runs hot, size up one frame.
Depth of 76 mm (70 mm installation depth) clears most shallow enclosures. Any mounting position is allowed, which simplifies layout in crowded cabinets.