in src/header.spec is section:
```
    for (i = 0; i < 3; i++) { // 3, 5, 205
      FIELD_RS (unknown_s[i], 0);
    }
```
Valid from AC1.50 to AC1009

I believe that this three values are numbers of ?, sections and header variables (idea, but i counted and seems that is).
On this values depends header variables (that's true).

3: ?
5: Number of sections (BLOCK, LAYER, STYLE, LTYPE, VIEW)
">=74 AND <=205": Number of header variables (from insertion_base, i don't know if 3d point is one or three)

In AC1.50 DWG files: 3, 5, 74; 3, 5, 83; 
In AC2.10 example (in [BLANK.DWG.gz](https://github.com/LibreDWG/libredwg/files/8088649/BLANK.DWG.gz)): 3, 5, 83
In AC1001 DWG files: 3, 5, 101
In AC1002 DWG files: 3, 5, 104; 3, 5, 114
In AC1003 DWG files: 3, 5, 120; 3, 5, 122
In AC1004 DWG files: 3, 5, 129
In AC1006 DWG files: 3, 5, 158; 3, 5, 160
In AC1009 DWG files: 3, 5, 204; 3, 5, 205
unknown_s[] fields in header
This is a GitHub Issue
repo:libredwg
owner:LibreDWG
Title : unknown_s[] fields in header
Issue date:

--- start body ---
in src/header.spec is section:
```
    for (i = 0; i < 3; i++) { // 3, 5, 205
      FIELD_RS (unknown_s[i], 0);
    }
```
Valid from AC1.50 to AC1009

I believe that this three values are numbers of ?, sections and header variables (idea, but i counted and seems that is).
On this values depends header variables (that's true).

3: ?
5: Number of sections (BLOCK, LAYER, STYLE, LTYPE, VIEW)
">=74 AND <=205": Number of header variables (from insertion_base, i don't know if 3d point is one or three)

In AC1.50 DWG files: 3, 5, 74; 3, 5, 83; 
In AC2.10 example (in [BLANK.DWG.gz](https://github.com/LibreDWG/libredwg/files/8088649/BLANK.DWG.gz)): 3, 5, 83
In AC1001 DWG files: 3, 5, 101
In AC1002 DWG files: 3, 5, 104; 3, 5, 114
In AC1003 DWG files: 3, 5, 120; 3, 5, 122
In AC1004 DWG files: 3, 5, 129
In AC1006 DWG files: 3, 5, 158; 3, 5, 160
In AC1009 DWG files: 3, 5, 204; 3, 5, 205
--- end body ---
