Table with summary start first day of each month

I use grafana v7.3.2 for monitoring power consomption.
I use prometheus for Data Source.

I am trying to configure a table with my power consumption.
I would like to have a summary of the month selected in absolute time starting with the first day of the month.
But I have a problem with the interval, if I do over a month it takes 30 days interval and therefore a shift in the first day selected.

I tried with a one day interval adding a transform but it also doesn’t work.

I just want a summary with the entire month selected that all.

Please help me
Thanks a lot