Not able to add values using the Form Calculation widget

I am following the instructions about using the Form Calculation Widget but no sum is appearing. I have enclosed a screen shot. Clearly I am not quite implementing this correctly. What does "0-9" mean? I am looking at the example, "How to Perform Form Calculations Using a Widget," but still no sum is appearing.

Hello! Your setup is correct. You only need to remove the extra '+' symbol (at the end of your formula) from your calculation and the calculation will start working (screenshot attached for your reference).

- Clearly I am not quite implementing this correctly. What does "0-9" mean?

"0-9" tells the form calculation widget to treat the values numerically. Similarly, "A-Z" telss the form calculation widget to treat the values alphabetically.

For example:
1. 10[0-9] + 20[0-9] will result in the value of 30
2. 10[A-Z] + 20[A-Z] will result in the value of 1020

I hope this makes sense. If you have any further questions, feel free to get back to us.