The Siemens 5SL4408-6 is a SENTRON-series miniature circuit breaker (MCB) — a 4-pole, 4-module-width unit with a B tripping curve, rated 8 A at 400 V AC.
The B-curve trips between 3 and 5 times rated current — so for this 8 A breaker, magnetic trip happens between 24 and 40 A. That makes it a good fit for resistive loads and general-purpose wiring where you don't expect high inrush; it's not the right choice for motor starting or transformer primaries where a C or D curve would be needed to avoid nuisance trips on inrush. Temperature derating is built into the spec: at 30 °C ambient it carries the full 8 A, but at 55 °C it's derated to 6.37 A. The 4-pole configuration (4P) switches all four poles simultaneously — line and neutral. That's typical for three-phase plus neutral distribution in European-style panels where you want a single device isolating the whole circuit. The neutral conductor is not switched separately, which is noted in the spec.