Binary operation (minus)

Using the latest grafana on Home-Assistant
Im having trouble with a calculation as shown in the picture. This speaks for itself.
The trouble seems something with the value
Thank you from the answers!

Try converting those 2 values to numeric using transformation and see if that changes things

Thank you for the answer, didnt do it except making both value as 0

Is the data coming from source with Kwh? Or is that something you sconfigured in grafana?

Both sensors are kWh

how were you able to add the 3rd element to the gauge visualization?