What the 1000 A rating means for your BOM line
Four poles (4P) handle three-phase plus neutral or a second load circuit.
Drawout mounting and panel fit
Drawout mounting means the chassis slides into a fixed cradle — you isolate and rack out the unit for maintenance without unbolting busbars. The footprint is 400 mm wide by 440 mm high by 560 mm deep. That 560 mm depth is the dimension from the mounting face to the rear of the chassis; verify your enclosure depth clears it with room for cable bending radius behind the cradle.