| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 11 |
1.1%
|
| 0 | 981 |
98.6%
|
|
| 20 | 1 |
0.1%
|
|
| 30 | 1 |
0.1%
|
|
| 40 | 1 |
0.1%
|