Due to the way the skin works, you can’t change the ranges through preferences.  Instead you’ll have to use a text editor.  Inside the Mustermann Iconic/classes folder, you will need to change the values for all the files inside the attributes folder and the dna folder.   In each file, you will need to edit the min_value and max_values to your desired ranges.  Let’s say for example, you wanted to increase the lowest range to 8, and then make the remaining bands be 4 attributes each.  You would set the first range from “1” to “8”, the second range would be “9” to “12”, the third range “13” to “16” and the final range “17” to “20”.  You would then need to repeat this for all the aforementioned files.  Once done, caching off, reload the skin.