Delete\Remove level with no name

I am supposed to clean up some drawings, there is an unused level shown: per example. I cannot delete in the level manager, find with the power selector. Not sure how to do a purge.. I made sure it was not selected to plot and that it was not locked.

    As shown there is a 6 in the example, not advanced enough to know how to remove

could send a copy of the file if someone wanted to test there theory on it ?