Image size problem with Retina Macbook Pro

I exported raw images to Jpg and then resized as 1200 x 800 resolution images through "Easy batch Pro" app. When I uploaded them, they were extremely large. I've tried it several times and the result was always the same. Is it a problem with "Easy batch Pro" app, or something with Retina Display resolution? I also resized them as small size like 600x400, but the image was totally broke, and apparently had different look when I saw the original via aperture. What should I do?