| Value | Category |
|---|---|
| 1 | Has certificate, seen |
| 2 | Has certificate, not seen |
| 3 | Has no certificate |
| 4 | Don't know whether has a certificate |
| 5 | No certificate, but registered |
| 6 | No certificate of DK , and not registered |
| 7 | No certificate or DK, and DK whether registered |