Library /sys$common/syshlp/helplib.hlb

 n

    The highest numbered header level whose title will be used as a
    subtitle. For example, if you enter .AUTOSUBTITLE 2, the titles
    of header levels 1 and 2 appear as running-head subtitles. Header
    levels 3, 4, 5, and 6 do not appear as running-head subtitles.

 +n

    Increases the current highest numbered header level by n.

 -n

    Decreases the current highest numbered header level by n.