ChartJS graph does not start at zero.

I am busy trying to build a monitor for my energy consumption and solar panels energy. It will be an internal app but for now it is open http://mycloudy.nl:8081 On tab two ‘Stroom Verbruik’ you can see that the first graph starts at four and not zero. I know how to solve this in javascript but not via the api. The programmer does not respond on my question so I ask it the this group. Who can help me. The graphs are made with the chartJS component for Vaadin 10.

Chris