Oceans and seas have elevations of 0, so for coast lines it is better to uncheck 'draw elevations with ZERO value'. In example, if you set minimum value for 1500ft and maximum for 1501ft you get bicolored image - blue color represents elevations =1501ft (pictured below). Other way to use those settings is to set them for path finding. Some areas can be pretty flat with single high peak, so it could be better to set maximum elevation manually to have better contrast in the flatter area. Minimum/Maximum elevations: when in AUTO mode, values here are the lowest and the highest elevations found and the colors range are spread along those. You can select either small area or entire country without changing any value (in AUTO mode). When you find optimal value for your system, you really don't need to worry about setting resolution value all over again.

If you have some performance hit, you can lower this value.

Optimal number of elevations is a threshold set by user for AUTO mode of resolution value. This is why radio buttons 'Calculate average value' and 'Find maximum value' are visible only when resolution is set to values greater than 1. Values are odd numbers and represent size of the area from input data, which is resampled into a single visible rectangle on map. Value of 1 is equivalent to the sample size of ~90 meters (depending of latitude). Resolution: lower values = higher resolution. Click right mouse button somewhere on the main map and select 'Add/Edit terrain layer' from popup menu.

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