How to move StringNumber along Y-axis?

[Arjan Bos]

Dear list,

How do I move the StringNumber to below the Staff? I tried Y-offset  
but that didn't work. As a test to see if I had the correct syntax, I  
tried the X-offset and that /did/ work. Any ideas?

\version "2.12.2"

\score {
  \relative c'' {
    %% This override does not move the StringNumber. X-offset does  
work!
    \override StringNumber #'Y-offset = #-10
    <c\3>1
    }}

MoveStringNumber.pdf
Description: Adobe PDF document

Kind regards,
Arjan Bos