Staff spacing snippet

[lilypond]

Is this snippet dysfunctional, or is it me? :)

http://lsr.dsi.unimi.it/LSR/Item?id=12

I get the same output for minimum-Y-extent -12, 12 as I do for 60, 60:

% http://lsr.dsi.unimi.it/LSR/Snippet?id=12

\version "2.14.2"

\header {
  tagline = ""
}

\score {
\new Staff {
  \override Staff.VerticalAxisGroup #'minimum-Y-extent = #'(-12 . 12)
  \repeat unfold 96 { c''8[ c''] } 
}
}

\layout {
   indent = 0\mm
}

http://umpquanet.com/james/snippet-12.pdf


% http://umpquanet.com/james/snippet-12a.ly

\version "2.14.2"

\header {
  tagline = ""
}

\score {
\new Staff {
  \override Staff.VerticalAxisGroup #'minimum-Y-extent = #'(-60 . 60)
  \repeat unfold 96 { c''8[ c''] } 
}
}

\layout {
   indent = 0\mm
}

http://umpquanet.com/james/snippet-12a.pdf

What am I doing wrong?

Thank you!

Jim