| Value | Category | Cases | |
|---|---|---|---|
| -998 | Dont know | 11 |
9.1%
|
| -888 | Other specify | 1 |
0.8%
|
| 1 | From 9 months to 5 years | 97 |
80.2%
|
| 2 | Every 6 months | 12 |
9.9%
|