This tool is designed to remove duplicate mark warnings from the Autodesk® Revit® files.

After running the command, select whether to remove duplicate mark warnings from: 

• Loadable families only.

• All selected families (need to select before running the tool)

After the selection, you can erase the mark value or you can give the numeric value sequence.

https://www.youtube.com/watch?v=VwZCeedP3QI