Soft Max and Min are software limits, you need to home the machine for them to be any use. If you do not have home switches you will need to manually jog to the fully negative on X and Y and fully positive on Z and then press Ref All button to tell Mach you are at Home Position.
Your Soft Min and Max forX and Y will be
Min = 0
Max = the axis travel distance
For Z it is the opposite,
Max will be 0
Min will be travel but as a negative number.
Hood