When you create a custom category, you must decide what type of data fields it will include. You can choose from the following category types:
You can create a custom data field called Historical Sigma in the multiple-entry category, X Variables.
You can create a custom data field called Region in a single-value category called Custom Project Data. Region is a list field, which contains a list of choices.
To create a list field that you can use in a formula, create a list field and assign values to the list options. Then create a formula field that uses the list values to calculate and display the result.