Magento属性值未正确保存

I am adding values to magento dropdown attribute programmatically. It saves the string values correctly no problems with that. But when add the value such as 30 or 50 or even 4D or 7D it is not saving these values which contains numbers or are integers. the code I am using is:

$arg_attribute = 'size';
    $attr_model = Mage::getModel('catalog/resource_eav_attribute');
    $attr = $attr_model->loadByCode('catalog_product', $arg_attribute);
    $attr_id = $attr->getAttributeId();
    $option['attribute_id'] = $attr_id;

    foreach($size_array as $size) {
        $found = false;
        foreach($options_array_size as $option1) {
            if($size == $option1['label']) {
                $found = true;
                break;
            }
        }

        if(!$found) {
            $option['value'][str_replace(' ','',"$size")][0] = "$size";
        }
    }

$setup = new Mage_Eav_Model_Entity_Setup('core_setup');
$setup->addAttributeOption($option);

Is there anything I am doing wrong here? What should I do to save the integers values in attribute options?