The left hand image sizes figure shows the flattened size of the image; this is how many bytes the image will take up when printed.
The right-hand figure shows the un-flattened size of the image, or the total space taken up by all the layers of the image. This is
approximately the size your file will be when saved as a .psd. If you have lots of layers in your image, the right-hand figure will be a
lot larger than the left!