History stats sensor + Statistics card

I have a history stats sensor defined to track how long my heating has been running for the day.
I would like to use the statistics card to show the average for This Month or This Week or something like that.
My impression is that if I use it and configure it to show “Mean” it will do an average of all the values (including 0h and up until the last value of the day, which is the one I actually want to use in the average) and not just using the highest number of each day.

Is there a better way to achieve this?

P.S. The switch entity for the heating doesn’t appear in the dropdown (and neither do the rest of mqtt entities)