Utility Meter - Help with Last Period Attribute

Hello,
In February, I set up an monthly based utility Meter for gas usage:

I guess it works as it should - resetting to 0 at the end of the month.
My intention was to compare this month with the one before, but why is the “last_period” attribute now 0? (I was expecting the last value of march)

Thanks for hints,
Philipp