The X Wings are sitting on an asteroid.
The VSD wants to use anti fighter attack does it lose a die, for the obstacle?
If it had only one die, does it not shoot?
If it was Tie Fighter shooting the X Wing, does it lose a die?
I think it loses the die, in both cases and can go to zero, but not sure, as under obstruction it just talks about shooting.
But the effect of obstacles on Squads hints I could be wrong.