Head back to Data Transformation.
Now you can see that we have 3 Data Transformation Lines.
The first line defines what operation will be done.
The second line defines on what the operation will be done - the input.
And the third line defines the output.
Note the Quantity column of the Transformation Lines. Make sure the values are the same as shown on the screenshot.
The very last step is to validate the Data Transformation.
Click on Validate on the left side panel to validate the Data Transformation.