Electrical Engineering - What is Icu & Ics indicated on the circuit breakers?

Question. What is Icu & Ics indicated on the circuit breakers?

Answer. Please see the below

Ultimate breaking capacity (Icu) is the maximum short-circuit current that a circuit breaker can break without damage. Icu is usually taken as symbol of quality for a specific voltage rating.

Service breaking capacity (Ics) is expressed as a percentage ratio of Icu and tells you the maximum short-circuit current if a circuit breaker can break three times and still resume normal service. The higher the lcs, the more reliable the circuit breaker.