The ABB S204-C4 is a 4-pole miniature circuit breaker (MCB) with a C-curve trip characteristic, rated at 4 A and 480Y/277 V.
The 4 A rating governs the continuous load; at 480Y/277 V three-phase, it protects a load drawing roughly 3.3 kVA. The 4-pole configuration (all poles switched) is typical for three-phase-plus-neutral circuits where you need full isolation on all conductors.