I didn't think it was working correctly either. Finally figured out that you need to enter the amounts in two boxes and not just one. Enter your amount in the top AND the bottom box:
| 2020 Form 8915E, line 9, if you checked the box on that line, enter 0 |
| 2020 Form 8915E, line 10 |
| 2020 Form 8915E, line 9 |
