Recipe from "emacs -nw -Q" (the "-nw" part is not strictly needed, but
it is cleaner for showing the problem):

1. Set the variable `scroll-step' to 3.
2. Visit the attached file.
3. Adjust the vertical space (empty lines) between "first line" and
"last visible line" until the latter becomes indeed the last visible
line in the window.
4. Move point to the "last visible line".
5. Move point two lines down in a single command: C-u 2 C-n

I observe that after step #5 the window is scrolled by `scroll-step'
lines (3 lines), which is TRT.

But if I set `scroll-conservatively' to 1 and repeat the experiment
(from step #4), then I observe that this time the line where point
goes to ("2") is centered in the window.

After reading (info "(emacs) Auto Scrolling"), I think that this is
either a bug in the program or in the documentation.  This paragraph
in particular doesn't match the observed behavior in the second case:

     The variable `scroll-step' determines how many lines to scroll the
  window when point moves off the screen.  If moving by that number of
  lines fails to bring point back into view, point is centered instead.
  The default value is zero, which causes point to always be centered
  after scrolling.



In GNU Emacs 24.3.50.1 (i386-mingw-nt6.1.7601)
 of 2012-11-04 on MS-W7-DANI
Bzr revision: 110794 rgm@gnu.org-20121104041313-7j1z7vaqtrgopt26
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --with-gcc (4.7) --no-opt --enable-checking --cflags
 -I../../libs/libXpm-3.5.10/include -I../../libs/libXpm-3.5.10/src
 -I../../libs/libpng-1.2.37-lib/include -I../../libs/zlib-1.2.5
 -I../../libs/giflib-4.1.4-1-lib/include
 -I../../libs/jpeg-6b-4-lib/include
 -I../../libs/tiff-3.8.2-1-lib/include
 -I../../libs/libxml2-2.7.8-w32-bin/include/libxml2
 -I../../libs/gnutls-3.0.9-w32-bin/include
 -I../../libs/libiconv-1.9.2-1-lib/include'

Important settings:
  value of $LANG: ESN
  locale-coding-system: cp1252
  default enable-multibyte-characters: t


-- 
Dani Moncayo