Statistics average_step on a binary sensor produces reverse of what I expect. Bug?

Hi there,

I have a binary sensor indicating when the burner of my heater is running. I’d like to have statistic that shows the percentage of time the burner was running in the last hour.

Here is my yaml:

- platform: statistics
  name: "oil burner running percent last hour"
  entity_id: binary_sensor.ol_brenner
  state_characteristic: average_step
    hours: 1
  sampling_size: 30

and here is the result.

It doesn’t make any sense to me. I’ve read the documentation over and over. What am I missing? This should be a straightforward use of the average_step function. Right?

What am I missing?