logger man page: update --size doc

now we have strict sizes

Signed-off-by: Karel Zak <kzak@redhat.com>
diff --git a/misc-utils/logger.1 b/misc-utils/logger.1
index b73f46a..164c5f4 100644
--- a/misc-utils/logger.1
+++ b/misc-utils/logger.1
@@ -97,10 +97,13 @@
 protocol. As such, the \fB\-\-size\fR option affects logger in
 all cases (not only when \fB\-\-rfc5424\fR was used).
-Note: the message size limit is not totally strict. It limits only
-the user data, the size of the syslog header is not considered. While
-this can lead to some truncation at the receiver level, a consistent limit
-based on the user data size is generally wanted.
+Note: the message size limit limits the overall message size, including
+the syslog header. Header sizes vary depending on options selected and hostname
+length. As a rule of thumb, headers are usually not longer than 50 to 80
+characters. When selecting maximum message size, it is important to ensure
+that the receiver supports the max size as well, otherwise messages may
+become truncated. Again, as a rule of thumb two to four KiB message size
+should generally be OK, whereas anything larger should be verified to work.
 .BR \-n , " \-\-server " \fIserver