Clamp a value and return 0.1 if its 3 or 3 if it 0.1 etc

I have a Drop system and each item have a weight i clamped the weight so its always returns 3 if item weight is greatear than 3 and 0.1 if is lower than 0.1 .

This script below is that what im searching but if i whant to change max value that is 3 or min value i need to change the entire code, the simplest way to do it?

private float DropForce (float num1)
{
        //Num1 is clamped item weight.
         if (num1 == 3)
         {
                num1 = 0.1f;
         }
         if (num1 ==  2.9f)
         {
                num1 = 0.2f;
         }
         if (num1 == 2.8f)
         {
                num1 == 0.3f;
         } 
// And the inverse

         if (num1 == 0.1f)
         {
                num1 == 3f;
         }
         if(num1  == 0.2)
         {
                num1 = 2.9f
         }
         //Etc
         return num1;
}

public float min = 0.1f;
public float max = 3.0f;

 float functionname(float input){
      float a = Mathf.Clamp(input, min, max);
      a = min + max - a;
      return a;
 }