code: public double getPluralOffset(int pluralStart) {
          Part part=parts.get(pluralStart);
          if(part.type.hasNumericValue()) {
              return getNumericValue(part);
          } else {
              return 0;
          }
      }
docs: Returns the "offset:" value of a PluralFormat argument, or 0 if none is specified.
  @param pluralStart the index of the first PluralFormat argument style part. (0..countParts()-1)
  @return the "offset:" value.
  @throws IndexOutOfBoundsException if pluralStart is outside the (0..countParts()-1) range