code: public void execute(
            TransformerImpl transformer)
              throws TransformerException
    {
  
      int sourceNode = transformer.getXPathContext().getCurrentNode();
      String countString = getCountString(transformer, sourceNode);
  
      try
      {
        transformer.getResultTreeHandler().characters(countString.toCharArray(),
                                                      0, countString.length());
      }
      catch(SAXException se)
      {
        throw new TransformerException(se);
      }
    }
docs: Execute an xsl:number instruction. The xsl:number element is
  used to insert a formatted number into the result tree.
  
  @param transformer non-null reference to the the current transform-time state.
  
  @throws TransformerException