In order to fully receive an item and have it be reflected properly in your inventory, a line item must fully be received. If an item it only partially received you need to enter the amount received in the received field and the amount of the item not received in the BO field. Once you click out of the BO field you will see a split icon just to the right of the item's name. Clicking on this icon will split the portion of the unreceived item into a new line item in order for you to fully receive it at a later time.
As will all POs, you still have to click the Post Receiving button in order for the items to enter inventory.