On the Synology OS (…some type of linux…) after editing the crontab you need to reload it otherwise no changes are made. /usr/syno/sbin/synoservicectl –reload crond

On the Synology version of Linux, you need to restart de Crontab (/etc/crontab/) to be able to apply the changes. To restart execute the following command. synoservicecfg –restart crond