If you now point at the menu item "System/Analyse", you will get the following result:
The required verification was not possible with the selected system configuration. Now go to the menu item "System/Optimise" and enter the following variation range:
Confirm with "OK". You will get this result:
Thus, in order to achieve an optimum utilisation factor, a 1.29 m thick clay liner is required. If you answer "Use ?" with "Yes", the system thickness determined here will be used as the new base in "Edit/Soils". The results shown in the legends are automatically adjusted.