Generate Custom Image Sizes - settings in Bricks

Does anyone know where I can find any documentation for this feature, in the Setting, General, Miscellaneous section? I realize what it might, or “should” do, but I cannot find any docs explaining this in detail, and I have a client bugging me about image sizes, as they are having a gallery issue, and I want to make sure the problem they are having is not a Bricks bug. Any docs on Bricks default image and thumbnail sizes either?