Graph Line Resolution is most useful on very very very slow computers. We don't imagine it to have a useful purpose, but it's there if you want it. The number for the resolution is the percent of pixels that are calculated on the line. Normally, every pixel across the graph is computed individually. If this takes too long, you can turn down the Line Resolution to, say, 20%, and the program will only compute every 5th pixel. This would only take one fifth as long. Of course having fewer pixels makes the graph look jagged, so you need to find a balance between speed and smoothness.