How to change max coverage?

I am having trouble changing the Max coverage. The max coverage is set at 8000, I want to change it to zero. I am going to : item details, set up , item coverage and following the wizard. In wizard: 

It will not allow me "delete invalid item coverage settings"

I  can "Create new item coverage "

I can input new max coverage at the inventory level screen. After click next on the Completed screen I  see a message "the wizard cannot create item coverage settings based on your selections"

Any help would be appreciated 

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I get to the final step and click finished and the max coverage remains the same.