You can find the sum of occurrences from 2 columns by using pivot.
Follow the below steps:
1. Add new data source (i.e the same source as before )
2. Now select the columns that you want to use to perform some.
3. Then click on the Drop-down button and click on the pivot.
4. Now click on sheet. Now place the pivot column and Drag the Number of records over the pivot field.
5. Now the occurrence among fields is shown in SUM(Number of fields) over the pivoted field (i.e multiple columns selected to count the sum of occurrences).
Hope it helps you.