Go into the library. Click on the Library Tab at the top. Click on Library Settings. All the way at the bottom, there will be views, click on the one that says "All Views."
The next page should give you all the columns that are available from your form. Click on the TestDDL column and choose the number where you want it to be. Click "Done" or "Save" button at the bottom of the form.
If TestDDL isn't an option to check, you need to go back to InfoPath and re-run the publishing wizard and add that column as a usable data source.
Hope this helps! :)