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once you calculate a map in bottom hardness
then press the up and down arrow (find depth Range) this will give u a upper and lower range number
use this formula for the gain
100 divided by the upper range number
(ie) say upper range is 50
100 divided by 50 = 2
this will be your gain
set fresh or salt water
set gain
set desired color
if u check 2d color layering then u can use the sliders on side of map to adjust transparency to see difference in two layers
ds