Did that testing, the conclusion was exactly what TGG said (well since he got it from the code that would be obvious lol):
// bottomOffset -> minimum height for the ore
// maximum -> minHeight + maximum = top level (the vertical expansion of the ore, it grows x levels from bottomOffset)
// topOffset -> subtracted from the maximum to give actual top level
// ore effectively exists from bottomOffset to (bottomOffset + maximum - topOffset)