I am trying to crop files in Camera Raw to several different file sizes. I use to be able to use the custom crop tool to crop to 640x800 pixels and save the jpgs and when I checked the properties on the file size, they would show the 640x800 size. Now this is not happening. What is the relationship between the custom crop tool and the Work Flow Options box?
The Custom Crop is setting an aspect ratio, where 640x800 = 8x10 = 4x5.
The Workflow Options are showing what your crop-ratio means in terms of the native image pixels, as a way to help understand how large it can be printed, or how large it would be if you saved it without resizing.
To create an image that is 640x800 pixels, besides setting the crop ratio to 4x5 or any equivalent ratio, you need to set the pixel dimensions in the Save Image dialog or within Photoshop if you use Open.