each Brightness/Contrast layer has a mask. i select the areas of my design or image where i want the Brightness/Contrast to apply, then invert the selection with ctrl+shift+i. with the Brightness/Contrast layer mask selected, i press the Backspace key to apply the effect only to the selected area. for the fourth Brightness layer, i held down ctrl+shift and clicked on the masks of my other layers to select the areas i didn’t want the effect applied to. then, i pressed Backspace to apply it to the fourth brightness layer. i hope that makes sense! if you have any more questions, feel free to ask on our discord server!