When there is a short circuit in the line and the breaker is closed, the peak value of the first cycle is the most severe from an electrodynamic perspective. This value is in kA. The making capacity is expressed as a peak value as the dc offset during fault conditions is taken into account.
Breaking capacity of the circuit breaker refers to the maximum current in rms value the circuit breaker can interrupt. This is also in the order of kA.
The making capacity of the circuit breaker is usually greater than the breaking capacity of a circuit breaker as breaking an electric circuit is difficult due to arcing which occurs and which has to be quenched.