I posted it as a suggestion because it wasn't clear to me at first that the bonus rewards was the second column; I initially thought that spending the kobans to press the 'unlock bonus rewards' button would open a second list of completion tasks and rewards, without indicating what those rewards would be. That's why I initially posted here under Suggestions that a description be included.
I did later realize that I had misunderstood how that game mechanic worked and that the button unlocked the second column. The fact that I had a face-palm moment and figured out on my own that I had just missed something obvious is why I had forgotten about my original post.
Slynia's reply was actually the most informative. I thanked MCP and Kenrae for providing clarification without mocking the fact that the answer to my question was there in plain sight, I had just hadn't paid close enough attention.