When a dispatch method is used the works order that is created is unusual in that the kit and the output batch represent the same product; for example a dispatch method is often used as a resizing operation or a ‘clean and pack’ operation.
The kit batch has the Packed flag un-set and the output batch has the Packed flag set. When a dispatch method is used, Match-IT allocates the same batch number, instance number and expiry date for both the kit and output batch (because in the real world they are the same thing).
If for some reason a dispatch method is not suitable (for example you require the kit and output materials to have different product codes) you can achieve the same behaviour by using derivitives.
If a material is marked as a derivitive of another, Match-IT takes this to mean that it represents the same real-world object, but has been (for example) resized or been cleaned and packed.
When Match-IT schedules a method step where the output material is a derivitive of the kit material it treats that step as if it were a dispatch method; i.e. the same batch number, instance number and expiry date are used for both the kit batch and output batch; even though in this case they have different product codes.
Note that in both cases if the kit batch is an existing batch the batch number, instance number and expiry date are propagated to the output batch.