Why do results of recovery contain less data than the original JPEG, GIF, TIFF, BMP, PNG or RAW image?
This is normal. The damaged parts of your JPEG, GIF, TIFF, BMP, PNG or RAW image will convert to zero size on output. The other common reason of file size decrease is when some of features of the original image are not supported and therefore absent from the recovered image. Demo-recovered image is smaller because it mostly consists of demo placeholders than actual data.