It means that you will see the slider in the controller ranging from 0 to 100% but the values will scale to the minimum and maximum you set there.
Ex: You set the minimum to 50% and the maximum to 90% of a controller that controls a fan. In the controller , 0% will set the fan to operate at 50% of its speed, and 100% to 90% speed of the fan.
That's what I thought but when I tried it had for instance a curve going from 45 to 100 but when i put like 40, the speed goes to 66%, why?