Periodically we're asked about how the default scaling on graphs is figured out by the system. It's actually a simple answer: For whatever time period you're graphing, we scale from the lowest number to the highest number. That's it!
Here's how it works out in practice:
When you create an entirely new statistic with no values, there's nothing to display. So you get an empty graph scaled from 0 to 1.
Entering the first value gives the graph something to look at. In this case where I've entered 25, the graph automatically scales from 24 to 26.
Now, as time goes on and higher and lower numbers are entered the graph will scale automatically to reflect that.
If the automatic scaling doesn't work out, you can override the scale. For more information about how to enter a custom scale and the effects of overriding the default, see the help article here: Custom Scale