Below the Curve Change graph, there are several sliders that represent different points in the tonal range:   

Slider

Tint In Range (non-flexo)

Tint In Range (flexo)

Most affectedAffectsMost affectedAffects
MindotDoes not appearDo not appearMindot Tint InMindot to 25%
Highlights10%0 to 25%10% to 15%Mindot to 25%
Quartertones25%0 to 50% 25%Mindot to 50%
Midtones50%0 to 100%50%Mindot to 100%
3/4-tones75%50 to 100%75%50 to 100%
Shadows90%75 to 100%90%75 to 100%

The value in the box under each slider is a change percentage. The graph appears flat until you make an adjustment.  Move the appropriate slider to adjust the corresponding tonal range or enter the tint out change percentage in the box under the slider.