public function real_grade_value($value, $max) {
        $localized = true;
        if (is_null($value) or $value === '') {
            return null;
        } elseif ($max == 0) {
            return 0;
        } else {
            return format_float($max * $value / 100, $this->gradedecimals, $localized);
        }
    }