Actually you have to make some modification to the code.
Type crontab -e, open your crontab file in your preferred editor, remove the line:
0 0 * * 0 ee site update --le=renew --all 2> /dev/null
and replace it with the following line:
0 0 1 * * ee site update --le=renew --all 2> /dev/null
Save the crontab file and exit the editor. The above command would check your LE certificates every month on the 1st and renew for all necessary EE sites.
Alternatively, you can add:
@monthly ee site update --le=renew --all 2> /dev/null
which is the same command with an easier syntax. You can then type crontab -l to view your crontab to ensure what you just added is actually there.