Here's how it works:
For a standard molded case circuit breaker, UL (and manufacturer) lists the minimum conductor size that can be used for that breaker. Regardless of anything else. This is necessary because the conductors act as a heat sink and the design of the thermal element in the breaker assumes a certain wire size.
This generally corresponds to NEC conductor ampacity assuming a current that is 80% of the breaker trip rating. NEC requires the conductor be sized at 100% of the intermittent load plus 125% of the continuous load, with "continuous" defined as 3 hours or longer. If all of the load is considered continuous, the resulting conductor size and breaker size is 125% of the continuous load. The inverse of 125% is 80%.
