code: void appendXMLAttributes(final XMLUtil util, final Appendable appendable) throws IOException {
  		util.appendAttribute(appendable, "number:decimal-places",
  				this.decimalPlaces);
  		this.numberStyle.appendNumberAttribute(util, appendable);
  	}
docs: Append number:decimal-places, number:min-integer-digits and number:grouping
  @param util an XML util
  @param appendable the appendable
  @throws IOException if an I/O error occurs