The build week is generated by the production planning software.
Your order is translated into a bill of materials (all of the parts needed to build that car) and then production planning uses on hand stock levels and lead times of parts not in stock to predict the point in time that it can be manufactured and book that into an available production slot on the assembly line. The parts are all called off and/or ordered when the slot is booked.
This is how just in time manufacturing works.
There are numerous things that can mean its sooner or later (if one part is available a week later then...) , its very complex and thats why you use software to do it :-)
It could be availability of the DSG gearbox or could be availability of ANY part or the lack of production slots available!
There might also be issues around dealer allocations...
