I'm confused about image size settings

I understand how to set the main album highlight size.
I understand how to set the album thumbnail size.
And I understand how to set the "resize" size.

But I'm confused about the Maximum Image Size. Currently it's set to 2048 (3M Pix). And there is a file size option too. I believe this Maximum Image Size refers to dimentsions but no sure. I can't see that this is doing anything.

But here's what I'd like to do

Have my largest image saved at no larger than 1024 pixels wide. So that would be... thumbnails at 150, resized image in album at 640 and my raw (largest) sized to 1024. Is that possible? Is that what the Maximum Image Size is supposed to do? If it is, it doesn't seem to work.

What does this (Maximum Image Size) do and how or what does it do? I thought it might be setting the size of my largest image but that doesn't seem to be the case.