Easy Tomato is a modified version of TomatoUSB, which is in turn a modified version of Jonathan Zarate’s excellent open source Tomato firmware. Relief Labs has worked to make this powerful firmware accessible to less technical users through easy to use documentation and a simplified interface
In Groups/Create Group page when a device is dragged out and then dropped back in the unassigned list, the device is cloned.
This seems like unexpected behaviour but doesn't appear have any real consequences.