That rating governs selectivity with downstream breakers: if your fault current at the panel main exceeds 70kA, this breaker is not the right frame. The TM220 thermal-magnetic trip unit gives adjustable overload protection (Ir) from 175 A to 250 A, and fixed short-circuit pickup at Ii = 10 x In.
The nut keeper kit (part of this ZD00 suffix) is specified for DC Power OEM builds in China, which means the breaker ships with captive hardware to simplify panel assembly in that supply chain. Verify the lug kit and busbar adapter match your panel layout before committing the BOM.