CalGraph is set so the y-values on the graph run from -5 to 5. You can easily change this.
To change the Range, click Customize and then Curve Domains/Range. Enter the lowest y-value you want in Ymin and the highest y-value you want in Ymax. Click Apply to see the difference. I often need several tries to get the Range the way I like it.
Once you are satisfied click OK or Close.