Negative values in a chart are not shown on Android App (and bad y-axis)

Hi,
I did a DataFiled with VerticalSpeed, which can be positive and negative.

1.
On Android the negative values are not visible, in the browser on the PC they are.

2. The formatting of the y-axis is also very bad. My values are rounded in steps of 50 (m/hours), the y-axis goes far to high myMax goes to 900 m/hour, but the axis is going till 2034!

Marcel