MechanicDesk's term for bringing items into stock from a purchase order is Process.
If the quantity of items received is less than the quantity ordered, an appropriate back order will be generated on this purchase order. In the below case, 2 items were ordered but only 1 was processed. Hence the tyre quantity on the current purchase order is adjusted to 1 and a back order numbered 15/1 is auto generated. It will have the remainder of the ordered tyres.