| Value | Category |
|---|---|
| -8 | Don't know |
| -1 | Missing |
| 1 | This term or during the preceding vacation |
| 2 | Last term of the previous school year (May August 2017) |
| 3 | Earlier than the last term of the previous school year (before May 2017) |
| 4 | It has not yet met |
| 2147483622 | |
| Sysmiss |