[V8] Does this servo look right?

[Seamus O'Carey]

I just received my replacement brake master cylinder and servo and it
doesn't look right to me.

First off, I'm not sure why it had to arrive disassembled in the first
place, but take a look at this pic and tell me what I'm missing.  Obviously
if the silver piece (master cylinder) has to fit all the way inside the
black piece (servo) then it won't work.  There is still at least half and
inch sticking out.  The diagram in the service manual doesn't show anything
in between them other than a rubber o-ring.
http://home.comcast.net/~lordseamus/AudiV8/brakeservo02.jpg

The part # on the master cylinder looks like it says 03 89 9154/12$17  (the
$ isn't exactly a real $, but looks kinda like one, but with two vertical
stripes instead of one).  The part # on the servo is 443 612 251 B


Also, how worried should I be about the little bit of rust inside the servo
housing?  I scraped off the rust and there's actually a little divot taken
out where the metal corroded away.  I'm not sure how worried I should be
about it, though, because it's in a place between two non-moving metal
parts.
http://home.comcast.net/~lordseamus/AudiV8/brakeservo01.jpg

What do you guys think?

Seamus