The startline and endline markup indicates the line breaks as defined by the formatting engine. The type of content in a line is indicated by the typemask attribute. The bits that may appear in a typemask indicate whether that content is plain or generated text, and are displayed in the following table:

If a line ends with a hyphen, the character code of the hyphen is added to the hyphen attribute on the end tag.

The margin where the line numbers appear in the printed output is defined by the value of attr2. Legal values are left or right. The default is right.

The quadding of the number, relative to the page center, is defined by the value of attr3. This value may be in or out. The default value is out.

The end of a line, where a break is no longer discretionary, may require special treatment. Set attr2 to fill on the end tag to end a line with a filler space that prevents an underfull error.