So, you are saying that after importing, the resulting GDL Object gives this message? Then I believe the conversion process was not successful if it resulted in a faulty GDL Object. Does the GDL Object appear in 2D or 3D? Is there any useful geometry generated?
GDL Objects have the Master Script, which is executed as part of other scripts, like the 2D script, 3D script. So probably the lines within the Master Script are also included in the Line Count. You would have to deduct the number of lines found in the Master Script to calculate which line in the 3D script LIne 521 is?
The info about the VERT command in GDL can be found here:
http://gdl.graphisoft.com/reference-guide/primitive-elements
Maybe if you ZIP the GDL file and post it here, we can take a look at it, but I am not certain it can be fixed if this is the state it is in right after conversion.
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