Formula Wizard Setup - By What Field

The "By What Field" feature in the Formula Wizard Setup requests you to select what the commission is based on: Quantity or Amount (in this example, or on any Unit of Measurement selected in the Data Element). 

Note:    The selection is dependent on the Data Element characteristics. 

Since the Data Element (1) includes products, the "By What Field" screen requests you to select the commission basis either by the Data Element UOMs. Proceed as follows:

1. Select the Data Element (1)
2. Select By What Field (2)
3. Click on Amount (3) or Quantity (4) or any other Unit of Measurement defined in the Data Element setup. Refer to article Creating a New Data Source. 
4. Press Next to move on to the next characteristic: Accumulation.

If, on the other hand, you select another Data Element (1) where there are no amount, the By What Field (2) screen includes the only available basis (here Quantity (3).