Invert the selected normal vectors.
Recalculate the selected normal vectors outside (Default direction) or inside (Inverted direction). If your object is set to Flat Shading the loop normals will be split, and if the object is set to Smooth Shading then the loop normals will be aligned.
This option resets the selected normal vectors to the original vectors when you started Abnormal.
For full destructive normal reset, please use Blender's default vector reset tool. In mesh edit mode, Mesh > Normals > Reset vectors