The Siemens 5SL4504-7 is a SENTRON miniature circuit breaker (MCB) — a 1P+N, 4 A, C-curve device rated for 230 V AC and a 10 kA breaking capacity per EN 60898 and IEC 60947-2. The C-curve trips between 5 and 10 times rated current (20–40 A for this 4 A unit), so it's sized for moderate inrush loads like small motors, pumps, and fluorescent lighting banks — not transformer or drive starts, which need a D-curve.
Temperature derating — the number that matters for real loading
At 40 °C it derates to 3.79 A; at 45 °C to 3.68 A; at 55 °C to 3.45 A. If your panel runs hot — near a drive bank or transformer — the 30 °C figure isn't what you size to. Use the 55 °C column for a worst-case continuous load of about 3.4 A.