The Grid type option in the Global Options dialog box applies only to curve data that specifies a reference axis with time line scaling. The reference axis in the graph of this curve is scaled by a time line.
This option allows you to specify the density of gridlines to be drawn in the background of the graph. Possible values, which are mutually exclusive, are:
Choose this value if you want no gridlines at all.
Choose the Coordinate grid value when you want gridlines drawn for each point in the graph: one line appears for each point's x-value.
Choose the Time grid value when you want gridlines drawn according to the time unit used in the time line.
This value activates the options Coarse or Fine under Time grid. If you don't choose the time grid type, you cannot set these options.