It's rated 125 A at 30 °C ambient, with a C tripping characteristic (magnetic trip at 5–10× In, typical for motor and lighting circuits with moderate inrush). The Type A fault-current detection means it catches sinusoidal AC and pulsating DC residual currents, which covers most modern electronic loads like VFDs, switched-mode supplies, and LED drivers. The 'selective' designation (S-type) means this RCBO has a deliberate short-time delay on the residual-current trip. It coordinates with downstream RCDs so that a fault on a sub-circuit trips the local device first, not this main switch. That's the difference between losing one branch and losing the whole distribution board.
The headline 125 A holds only at 30 °C. At 40 °C it's 115.62 A; at 45 °C it's 111.25 A; at 50 °C it's 106.25 A; at 55 °C it's 101.25 A; at 60 °C it's 96.25 A. The 4-pole package dissipates heat from all three phases plus the neutral, so grouping several of these in a row without ventilation gaps will push the effective ambient higher.
Width is 198 mm, which is 11 width units at 18 mm per module — that's a wide device, so plan for it in your rail layout. Height is 90 mm. Touch protection is built in (fingertip-safe terminals per the product feature).