In this video, you'll learn how to set the trigger area. 

First, we go to Options and Set Trigger Area. We can use the Auto Find feature and click Finish. Make sure the crosshair is inside the Trigger Area.

We can also set the Trigger Area without the scale. 

If the Auto Find feature does not work well, we can manually drag the borders to adjust and set the Trigger Area. 

This is how you can set Trigger Area.