Hi,
You would have to change the line:
$extraFilters = array('order_status' => '', 'order_range' => 'last 6 months');
to:
$extraFilters = array('order_status' => '', 'order_range' => '');
in the file components/com_hikashop/views/order/view.html.php
We'll also add a hidden setting with the namekey orders_listing_default_range in the next version so that you can add an entry with that namekey and an empty value in the hikashop_config table via phpmyadmin to be able to set that without having to modify the code.