Assuming it was generated using GNU tools on Linux, both the header and the footer are specified together as arguments to the
.TH macro. From
man 7 groff_man:
.TH title section
[footer-middle] [footer-outside] [header-middle] Define the
title of the man page as title and the section as section.
See man(1) for details on the section numbers and suffixes
applicable to your system. title and section are positioned
together at the left and right in the header line (with
section in parentheses immediately appended to title).
footer-middle is centered in the footer line. footer-outside
is positioned at the left in the footer line (or at the left
on even pages and at the right on odd pages if double-sided
printing is active). header-middle is centered in the header
line. If section is a simple integer between 1 and 9
(inclusive), or is exactly “3p”, there is no need to specify
header-middle; the macro package will supply text for it.
And the rest of the convention is given in
man 7 man-pages:
The first command in a man page should be a TH command:
.TH title section date source manual
title The title of the man page, written in all caps
section The section number in which the man page should be
placed (e.g., 7).
date The date of the last nontrivial change that was made
to the man page. (Within the man-pages project, the
necessary updates to these timestamps are handled
automatically by scripts, so there is no need to
manually update them as part of a patch.) Dates
should be written in the form YYYY-MM-DD.
source The source of the command, function, or system call.
For those few man-pages pages in Sections 1 and 8,
probably you just want to write GNU.
For system calls, just write Linux. (An earlier
practice was to write the version number of the
kernel from which the manual page was being
written/checked. However, this was never done
consistently, and so was probably worse than
including no version number. Henceforth, avoid
including a version number.)
For library calls that are part of glibc or one of
the other common GNU libraries, just use GNU C
Library, GNU, or an empty string.
For Section 4 pages, use Linux.
In cases of doubt, just write Linux, or GNU.
manual The title of the manual (e.g., for Section 2 and 3
pages in the man-pages package, use Linux