You need to decide if the expo should be setup in you radio, or in software. There is a checkbox in the controller editor (Select Controller... / Edit), "Enable Software Radio Dual Rates and Expo". If the is checked, the expo is done in software, and as mentioned above this can be configured in the model editor.
However, if the that checkbox is unchecked, expo should be set in your radio, and the software will not apply any expo.
If you change expo in your radio but the box is checked, results are unpredictable.