Crossed line over style icon

[Elizabeth Holloway]

Hey, while working it seems that I accidentally did something to this black #1 style, which I circled below, that added a little white diagonal line across it in the palette.  Does anyone know what that is supposed to indicate?  Is it something that I would want to undo, and if so, how?  (This is the style I was using for outlines and it's in a Toonz Raster level)