Parcels often come in with waybill barcode. Normally if its a single parcel for that waybill you can just scan the barcode to log it in then and deliver it using the waybill number. However when more than one parcel is on the courier waybill you need to associate the same waybill number with each parcel but differentiate between them when they deliver. On the other hand you may also want to 'deliver' all the parcels on the same waybill to a drop off point just scanning the waybill number once and automatically recording the total parcels delivered .