Navigate to Reports > Builder > Charts
Choose a Chart you wish to update, from the overflow menu select Customise Template:
This will open the template in a new tab on your browser.
Click in the chart display area in the center of the screen
Click the Run Designer at the top right of the display area
In the left controls, expand Diagram
Select Primary Axis Y
In Properties on the Right side:
Expand Visual Range > untick Auto > untick Auto Side Margin
Expand Whole Range > untick Auto > untick Auto Side Margin
Min Value > type your required start value
Max Value > type your required maximum value, click into white space
Check the display in the center of the screen updates to your values, and click OK
Check the Chart Display has also updated to your values
Click the three horizontal lines at the top left of the screen, and SAVE
Go back a tab in your browser to the Chart, and click Refresh