Available to Reserve in On hand quantities form is not matching with the value returned by INV_QUANT

Hi

We are testing below script two get On hand quantity and quantity reserved already.  Finally, We want to derive Nett Quantity that is available to transact. 

But, for Non controlled items (neither lot controlled nor serial controlled), below API is returning quantity reserved (x_qr) as zero even though there are reservations exists.  Where as Quantity On Hand form is showing correct quantity reserved.

Am I missing any thing or is there any bug?

DECLARE

                                    p_item_id              NUMBER;

                                    p_org_id              NUMBER;

                                    p_subinv              VARCHAR2(20);

                                    x_qoh              NUMBER;

                                    x_qr               NUMBER;

                                    x_return_status    VARCHAR2(10);

                                    x_msg_data         VARCHAR2(4000);