form edit and % arguments

Hello
I'm building my first module and I'm stuck with my 'edit' form.
I create a Holidays period with 2 dates (beginning day-finishing day). It looks like this:
------------------------------------------
Holidays management

Starting day Ending day Operations
1/10/2011 5/10/2011 edit delete
2/11/2011 5/11/2011 edit delete

Add a Holidays period
------------------------------------------

I've succeeded to create my 'add' form.
Looking through the uc_attributes module I similarly built a menu item

function cart_scheduler_menu() {
...
// menu edit Holiday period
 $items['admin/store/Cart_scheduler/Holidays/%id/edit'] = array(
    'title' => 'Edit Holiday Period',
    'description' => 'cart_scheduler settings',
    'page callback' => 'drupal_get_form',
	'page arguments' => array('cart_scheduler_holidays_add_form'),
    'access arguments' => array('administer Cart Scheduler'),
    'type' => MENU_CALLBACK,
  );
// menu add Holiday period
  $items['admin/store/Cart_scheduler/Holidays/add'] = array(
    'title' => 'Add a new Holidays Period',
    'description' => 'cart_scheduler settings',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('cart_scheduler_holidays_add_form'),
    'access arguments' => array('administer Cart Scheduler'),
    'type' => MENU_NORMAL_ITEM,
  );
...
}

and defined those 2 links 'edit' - 'delete' on each row of my table like this:

function cart_scheduler_holidays_page(){
$holidays= db_query("SELECT a.* ....
while ($data = db_fetch_object($holidays)){
$ops = array(
      l(t('edit'), 'admin/store/Cart_scheduler/Holidays/'. $data->id .'/edit'),
      l(t('delete'), 'admin/store/Cart_scheduler/Holidays/'. $data->id .'/delete')
   }
}...

and my add-edit form is:

function cart_scheduler_holidays_add_form(&$form_state,$holidays =NULL) {
if (!empty($holidays)) {
    $form['id'] = array('#type' => 'hidden', '#value' => $holidays->id);
    drupal_set_title(t('Edit holidays: %ide', array('%ide' => $holidays->id)));
}
$form['starting_day'] = array(
    '#type' => 'textfield',
    '#title' => t('Beginning day'),
    '#description' => t('Beginning day'),
    '#default_value' => !empty($holidays)? $holidays->starting_day : 1,
    '#required' => TRUE,
  );
etc
  }

But when I'm clicking on edit it sucks ! It stays on same page .
I'm pretty newbie in Drupal Dev and I dont understand how 'page arguments' works.
in uc_attribute module, this params displays :

$items['admin/store/attributes/add'] = array(
   ...
    'page callback' => 'drupal_get_form',
    'page arguments' => array('uc_attribute_form'),

$items['admin/store/attributes/%uc_attribute/edit'] = array (
    'page callback' => 'drupal_get_form',  
    'page arguments' => array('uc_attribute_form', 3),

What is this little '3' ? Is it in relation with the fact that the same form called, switch in edit mode rather than add mode ? It seems that is no test against it in the
function uc_attribute_form($form_state, $attribute = NULL)
I've strictly copy their code but mine sucks!
Did I miss some param, something else ?
Didnt find any help nowhere about those '%, form, edit, add' and so on...
:-)