specifies the size of the grid first pair is NX & NY of the grid you want to produce second pair is the size of the grid that was originally created each needs to be an integer multiple of the corresponding entry of the first pair. Note that for double-null cases, the interior guard cells corresponding to the top divertor boundaries should not be multiplied.
at least 100 additional numbers, of which only the first is relevant, unless using an analytic formulation for the grid. A value of -1.0 asks to read the mesh data using the "simplified" Carre format. A value of -2.0 asks to read the mesh data using the Sonnet format. A value of -3.0 reads the geometry information for a linear device.