no, you are using the proma - Mach has no knowledge of your voltage etc - ALL height control is done via the Proma, mach simply controls the motion in XYZ, nothing more.
you set the voltage on the proma but before you do that you need to know what voltage you desire.
this means test cuts - straight cuts about 150 - 200 mm long, set the height manually as per torch manufacturer specs using feeler gauges etc and then set mach to cut at the speed recommended or the speed you deem it will cut properly.
now you need to make a test cut and watch the voltage on the proma - it will jump about a bit but should settle long enough to get an average reading, say its 150v for example.
when the cut finishes, dial in 150v on the proma, connect the up/down signals etc so the proma is talking to mach, then when you make the next cut, the proma should try its hardest to move the torch height to maintain the set voltage +/- a small dead-band which i think is adjustable.
that is basically it, but DON'T FORGET, the voltage you have just set is ONLY correct for that thickness metal AND at that speed - change either one and you need to get a new voltage by the same methods, soon you will have a list of voltages, thicknesses and speeds and can simply dial in what ever metal you are cutting.
There are more complex THCs and these DO have the voltages on the mach screen etc but i think the cheapest one is going to be up in the £700-900 range