* The distant meters are no longer needed. Delete them
* The white spot is still build of triangles instead of a primitive
* Select the Surface Mode (F3) in the 3D editor
* Select all white triangles of the oval by holding the CTRL key
* Delete 'em
* Select the Subpart Mode (F5) in the 3D Editor
* Select the dark grey ndis.dat prim in the 3D Editor
* Select Show Selection in Text Editor in the 3D Editor
* The corresponding line in the Text Editor will be highlighted
* Copy the line 1 72 -12.3874 0 1.9697 0.5084634 0 0.2552473 0 1 0 -0.1362423 0 0.952596 4-4ndis.dat in the Text Editor
* Past the line just below
* The "Problems" pane will prompt a "Duplicated lines?"
* In the Text Editor change one of the two "4-4ndis.dat" to "4-4disc.dat"
* The error in the "Problems" pane disapears
* Color the new prim white either via the color icon bar or by changing the color number 72 (Dark Bluish Grey) to 15 (white)
Screenshot
LEGO ergo sum