IEF Display Order/Delta?

I've got a module I'm developing where I'm adding a field from an entity - which looks like this (so far)

function customized_inline_entity_form_table_fields_alter(&$fields, $context) {
    // Make sure there's a stock field on each of the allowed product types.
    $is_tender_detail = FALSE;
    foreach ($context['allowed_bundles'] as $bundle) {
      if ($bundle=='rate') {
        $is_rate = TRUE;
      }
    }
    if ($is_rate) {
      $fields['field_rate_dates'] = array(                   // This part adds the body field with a label 'description'
        'type' => 'field',
        'label' => t('Dates'),
        'weight' => 101,
      );
    }
}

As you can tell I'm just adding the data from field_rate_dates to the table. I'd *like* to have the output ordered by the date - but it looks like IEF is just setting the order randomly. Even if I attempt to manually set the delta-value - it gets ignored.

Anyone have any hint on how to automatically sort the output by the value of field_rate_dates?

Thanks!