Have a look at https://en.wikipedia.org/wiki/Cron#Overview.
In short: At 00:00 hours on 19/07 (i.e. July 19) execute that command. The * means 'regardless of what day of the week it is'.
In short: At 00:00 hours on 19/07 (i.e. July 19) execute that command. The * means 'regardless of what day of the week it is'.
[Edit:] What the... Nope, sorry, seems you're right and I'm wrong -- weekly it is. [/Edit]