What the ratings mean for fit
The 5SU1653-0KV06 is a combined residual-current and miniature circuit breaker (RCBO) — one unit does both ground-fault and overcurrent protection. The B-curve 6A rating means it trips magnetically at 3–5× rated current (18–30 A), sized for resistive or lightly inductive loads like lighting or control transformers. The 300 mA residual sensitivity (Type AC, sinusoidal AC only) covers general socket circuits where a 30 mA unit would nuisance-trip on leakage; it's not for personal shock protection — that needs 30 mA or less. The 4.5 kA breaking capacity at 1+N-pole handles typical domestic or light commercial fault levels. The 70 mm width (4 DIN modules) fits a standard DIN-rail enclosure.
Where it goes in the panel
Snap-on DIN-rail mount for standard 35 mm rail. The 70 mm width (4 modules) means it occupies four adjacent positions in a consumer unit or distribution board. The 1+N-pole configuration switches the line and provides neutral disconnect — verify the neutral bar arrangement in your panel, as some older boards use a solid neutral bus that needs bridging.