I'm having hard time figure out the format to run every hour on the :50 minute mark.
Timer unit lacks value setting. Refusing.
You can find detailed description how to specify time for timer unit in
Examples for valid timestamps and their normalized form: hourly → *-*-* *:00:00
So I guess the value you want to put there is:
Either time or date specification may be omitted, in which case the current day and 00:00:00 is implied, respectively. If the second component is not specified, ":00" is assumed.
So it should be enough to put there just