Hi pat. The steps are for AA purposes. Usually in conjunction with a 20mm Oerlikon gun. The lower down the steps the gun crew went, the higher the firing angle that can be obtained with reasonable comfort...

To assist with elevation and depression of the gun.

Hi Pat, I don't know the answer, so I'll try a hypothesis.
The steps are designed to allow soldiers of different heights to comfortably hold and swing the cannon.
A very short soldier will stand on the outer circle. A very tall soldier will stand on the inner circle.
A soldier of average height will stand on the middle circle.
The only problem is the distance from the cannon.
This system would work if the cannon mount had a system to move it back or forward to compensate for the approach or departure from one circle rather than another.
I'm not sure if I've managed to explain myself clearly.
Finally, I think the circle system could be useful for the soldier who needs to stand in place but can sit (obviously not when using the weapon).
It's preferable (once their usefulness has been established) to have steps that go down rather than up, for obvious reasons.

My guess is that it is for the gunner to step down making it easier to train on higher flying targets....elevation. 🤞