The In rating is 25 A, with overload protection Ir fixed at 25 A and short-circuit protection Ii set at 12.8 x In — that is 320 A magnetic pickup. This is a standard IEC 60947-2 device, so the 55 kA rating is the ultimate short-circuit breaking capacity — the maximum fault the breaker can clear once and remain functional afterward.
The nut keeper kit noted in the description (for DC Power OEM in China) suggests the unit ships with hardware intended for a specific OEM assembly — verify the kit contents if you are integrating into a standard Siemens 3VA1 panelboard rather than a captive OEM build. The 3-pole configuration suits three-phase line protection for feeders, branch circuits, or downstream sub-distribution.