The default format of a wire number is defined in the AutoCAD Electrical toolset Project Properties dialog box. This format is used for all wire numbers inserted on a drawing. However, there are times when you want certain types of wires to be numbered in a different way (that is, to carry a different format). AutoCAD Electrical toolset allows you to override the default wire number format by using layer defined formats. For example, your default wire number format is %N. It takes on the line reference number (in Reference Mode) or the sequential number (in Sequential Mode). If there are multiple wire numbers on a particular line reference a suffix is used from the defined suffix list to make the wire number unique.