You can define the way contours are displayed. The contour is defined by a Primary option that defines the contour type and a Secondary option that depends on the primary option.
You can choose to see the contours as "boxes", following the grid cells, or you can smooth them by choosing "shading". The "shading" option shows different layers in different colours. If you choose "no contour", you must choose "Draw isolines" to be able to see anything at all. The isolines are lines on which the value is the same. You can see this value by choosing "With labels".
When you choose "Shading" or "Box contours", you can also plot the color legend. The color legend can be configured using the Palette wizard. You can create, open, edit and save a palette file. You can use the dialog to calculate the limits from the data file by pressing "calculate", or you can specify the limits yourself.
If you select ‘<New levels/colors...>", you can define a custom palette which is either "Auto scaled" or "Fixed". On the fixed palettes, you can specify the data value ranges. (For a "land/water fixed palette" you only specify the lower limit, while the upper limit is the land value).