I figured it out

NLinearScaleConfigurator scale = new NLinearScaleConfigurator();
    scale.LabelValueFormatter = new NNumericValueFormatter("0.0##E+00");
    heatMap.Legend.PaletteScaleConfigurator = scale;

I have a heat map where the legend prints only 0 on the legend - actual numeric values work OK on the heat map (they display correct color values). The problems is the range of values is from 1e-9 to 1e-14. The legend simply displays each range as 0. 

I would like to change the numeric format to 0.0##e00  - but have not been able to find a Numeric format accessor class for the legend numeric display like where I could use NNumericValueFormatter("0.0##E+00");