private function freePercentCalculation(array $usedPercent = array()) {
        $aReturn = array();
        foreach ($usedPercent as $keyUsedPercent => $valueUsedPercent) {
            $aReturn[$keyUsedPercent] = ($valueUsedPercent > 0) ? (100 - $valueUsedPercent): 100;
        }
        return $aReturn;
    }