Comment 3 for bug 234926

Here is an excerpt from /usr/share/doc/logwatch/HOWTO-Customize-LogWatch.gz

You can customize the output of logwatch by modifying variables in the
/etc/logwatch/conf directory.

Default values are specified in the /usr/share/logwatch/default.conf
directory. Your distribution may have set additional defaults in the
/usr/share/logwatch/dist.conf directory. All the variables available
are declared in the files under these directories. You can change the
default values to modify how or what is displayed with logwatch.

One variable available to all services, and which by default is not
specified, is the 'Detail' variable (note that it is not preceded by
a '$' symbol). Specifying a Detail value will override the global
Detail level, for that service only.

There are two mechanisms for customizing the variables:

1. The /etc/logwatch/conf directory is first searched for files with the
   same name and relative location as the
   /usr/share/logwatch/default.conf directory. Variables declared in
   these files override the defaults.

   For example, if file /etc/logwatch/conf/services/sendmail.conf has the
   single entry:
        $sendmail_unknownusersthreshold = 5
   then the threshold for unknown users is set to five instead of the
   default of one. All other parameters are not modified.

and so on.
     If you read that , your question is answered.