| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 6 |
1.1%
|
| 1 | Higher than usual | 18 |
3.2%
|
| 2 | Lower than usual | 21 |
3.8%
|
| 3 | The usual | 509 |
91.9%
|