df will try harder to elide file systems insignificant to the total
available space, by suppressing duplicate remote file systems.
-For the grand total line, @command{df} prints @samp{"total"} into the
-@var{source} column, and @samp{"-"} into the @var{target} column.
+For the grand total line, @command{df} prints @samp{total} into the
+@var{source} column, and @samp{-} into the @var{target} column.
If there is no @var{source} column (see @option{--output}), then
-@command{df} prints @samp{"total"} into the @var{target} column,
+@command{df} prints @samp{total} into the @var{target} column,
if present.
@item -t @var{fstype}