100

Subclass marker (AcDbXline)

10

First point (in WCS). DXF: X value; APP: 3D point

20, 30

DXF: Y and Z values of first point (in WCS)

11

Unit direction vector (in WCS).
DXF: X value; APP: 3D vector.

21, 31

DXF: Y and Z values of unit direction vector (in WCS)