jpegtran lossless rotation?

[Victor Munoz <vmunoz@macul.ciencias.uchile.cl>]

Hello. I'm a bit confused. jpegtran is supposed to provide lossless 
transformation on jpg files. Understanding nothing about the internals of 
graphic formats, I'd expect that original and transformed files had the same
number of bytes. However, if I apply it to some file from my digital camera,
the command:

jpegtran -rotate 90 -copy all pict0069.jpg > l.jpg

yields:

-rw-r--r--    1 vmunoz   vmunoz     436513 Jan 24 19:06 l.jpg
-r--r--r--    1 vmunoz   vmunoz     440635 Jan 24 18:39 pict0069.jpg

which is almost the same. Does anybody know where do the 'lost' bytes belong
to? Exif data? I checked 'exif l.jpg', and 'exif pict0069.jpg', and 
the output is exactly the same. 

I know I'm being obsessive, but does anyone know?

Regards,
						Victor