TOPIC: Ad Group Number Column in Cart

I would like to add a column to display the group number in the shopping cart at checkout, I have the column created here: components/com_dtregister/views/event/tmpl/viewcart_row.php and I have added this line,

<?php echo $type[$this->registration];?>

however I do not know what the label should be to call up this information (actually I do not really know what the PHP code should be either). Please help?