$quantity_stored = $this->db->map_unique('item_serial', $item_serial, 'item_quantity', 'item', false);
if(!is_numeric($quantity_stored)) $quantity_stored = 0;
$item_quantity = $quantity_stored - $quantity_removed;
$quantity_stored = $this->db->map_unique('item_serial', $item_serial, 'item_quantity', 'item', false);
if(!is_numeric($quantity_stored)) $quantity_stored = 0;
$item_quantity = $quantity_stored - $quantity_removed;