Create custom attribute for specifi product

i’m tring to create a custom attribute only for a specific product.
Into apply_to field i have setted a list “configurable, grouped” , a array(‘configurable’, ‘grouped’) or single type, but doesn’t work fine

what is the problem?

    <?php

$installer = $this;

$installer->startSetup();


$this->addAttribute('catalog_product', 'project_test3', array(
'type'              => 'text',  
'input'             => 'text',
'label'             => 'Project TEST3',
'backend'           => '',
'visible'           => true,
'required'          => false,
'visible_on_front'  => true,
'apply_to'          => 'configurable')); $this->endSetup(); ?>