Your syntax is incorrect for setting a Value Labels. If the RmG column is character, the label should be set with:
Column( dt, "RmG" ) << Value Labels( {"0%" = " "} );
However, I suspect the RmG column might be a numeric column, and if so, the label should be set with:
Column( dt, "RmG" ) << Value Labels( { 0 = " "} );
Jim