| Offsets | Name | Length | Format | Description | |
|---|---|---|---|---|---|
| 0 | SMF99_IOSUB_BW | 4 | binary | Bucket width. | |
| 4 | 4 | SMF99_IOSUB_LSTX | 4 | binary | Last plotted x bucket. |
| 8 | 8 | * | 4 | binary | Reserved. |
| 12 | C | SMF99_IOSUB _POINTS_OF | 4 | binary | Offset of point entries. |
| 16 | 10 | SMF99_IOSUB _POINTS_ON | 2 | binary | Number of point entries. |
| 18 | 12 | SMF99_IOSUB _POINTS_LN | 2 | binary | Length of a point entry. |