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 for us -1.0 read the mesh data using the "simplified" Carre format -2.0 read the mesh data using the Sonnet format