Hi Eluze,
I'm not at my computer to check my actual code, but it is only trivially different from the snippet I linked from the lilypond documentation (copied here):
<<
\context Voice = "foo" {
\clef bass
c4 r g r
c4 r g r
c4 r g r
c4 r g r
}
\context Voice = "foo" {
\set countPercentRepeats = ##t
\override PercentRepeat #'transparent = ##t
\override PercentRepeatCounter #'staff-padding = #1
\repeat percent 4 { s1 }
}
>>
Is that enough? As the png http://www.lilypond.org/doc/v2.16/Documentation/e2/lily-2580fe78.png shows - numbering starts at 2 on the second bar in that example.
Many thanks