| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 4 |
3.6%
|
| 0 | 99 |
89.2%
|
|
| 10 | 2 |
1.8%
|
|
| 20 | 5 |
4.5%
|
|
| 30 | 1 |
0.9%
|