When you create your own image using DOS you get the the numbers from DOS that I have used for 2GB, and it works as I have full 2GB in use. The codes you are showing probably work too or maybe not without trying them out.

If you look at what you posted:

256MB image: 512,63,16,520
512MB image: 512,63,32,520
1GB image: 512,63,64,520

and my 2GB Image

2GB image: 512,63,128,520

It follows the same logic. Thats why I am not sure about what is posted with 1023 as the last digits without trying it?

I think what you have with this:

2GB image: 512,63,64,1023

Is maybe a 2.08 GB Image

This is what I thought was important when I did the image:

Please notice that you can name the image whatever you would like. You may also vary the size as you wish. However, FAT16 file system has a hard disk size limit of 2 GB, so you have no reason to go larger

Regards
Nick