The plugin currently puts the order number in the Invoice # field and the website name in the Description field.
As far as I’m aware, WooCommerce does not have a concept of an “invoice number”.
You can customize the data sent to Authorize.net using the woo_mp_authorize_net_charge_request
filter, like so:
/** @param \WC_Order $order */
add_filter( 'woo_mp_authorize_net_charge_request', function ( $request, $order ) {
$request['createTransactionRequest']['transactionRequest']['order']['invoiceNumber'] = 'Put something else here...';
$request['createTransactionRequest']['transactionRequest']['order']['description'] = $order->get_order_number();
return $request;
}, 10, 2 );
If you have some plugin that assigns invoice numbers to orders, you can put that where it says “Put something else here…”.