Hello
This is essentially a make-to-order stock. It means that, for the finished product, you will not consider the existing stock.
For the components, however, you can control if the will be linked to the sales order stock using the individual/collective setting of the material master. If you set the value 2, system will plan the components as MTS and it will consume the existing stock before creating a new replenishment proposal.
BR
Caetano