Change the box size ; set to 10 rather 10.002

Data/prolate50.fma

 8 4
-20  10.002   0.0   0.0  0.0 
+20  10.00   0.0   0.0  0.0 
 -0.381596       -0.909478       -1.65028       7.82637e-06
 -0.328097       -0.475796       -8.1607       0.131538
 0.773946       -0.488975       4.02381       0.755605