Circuit Breaker Selection using IEC 60909

A1) Use the appropriate national electrical standard. In the UK, for example, it is BS7671.

A2) If in doubt, consult a qualified local Electrician, who will be able to calculate, install, test and certify when complete.

03 Short-circuit current characteristics.

https://new.abb.com/news/detail/11829/defining-short-circuit-values-for-circuit-breakers

Older Yanks use ANSI values, as those were the ones the equipment was tested to, using terms as shown by SE in his reply.

In broad terms, ANSI C37, I believe,

The medium and higher voltage equipment was tested for momentary withstand, which includes the asymmetrical component, and the interrupting rating had to exceed the value the system could deliver at the time of interruption, for instance 2Hz or 5Hz from sensing of 3 phase bolted fault with all generation on line. The X/R ratio is calculated from local generation values, using the subtransient reactance of the connected machines.

For low voltage, <600V, the interruption value is taken to be the symmetrical value only, braced for the asymmetrical forces.

One could always discuss <...the short circuit results...> with the <...circuit breaker...> supplier. Telephone, perhaps?