Dashes indicate settings that apply to only part of a selection.
In a mutually exclusive attribute or action group of commands, only one item is in effect at any one time. In a menu, use a checkmark to indicate the item that's in effect. For example, the Left, Center, and Right commands in a graphics menu are a set of three commands, only one of which can be in effect at any time. A checkmark indicates which item is in effect for the current selection. When the user chooses a new menu item, move the checkmark to that item.