fix varname in cronjob file

docs/40_Usage/40_Cronjob.md

@@ -50,14 +50,14 @@ $ cat /etc/cron.d/client-backup
 If you don't run the backup on a server but on a client you can activate the desktop notification for a user that is logged in. It uses *notify-send* to show notification messages.
 
 In a cronjob that start the backup script as root must know the user that should get the notifications.
-Set a variable `SUPER_USER=<USERNAME>` in your cron file.
+Set a variable `SUDO_USER=<USERNAME>` in your cron file.
 
 Example:
 
 ```shell
 $ cat /etc/cron.d/client-backup 
 
-SUPER_USER=axel
+SUDO_USER=axel
 
 17 * * * * root /usr/local/bin/cronwrapper.sh 1440 /opt/imlbackup/client/backup.sh 'iml-backup'
 ```