The inventory assigned to the marketplace will always be the one defined by the seller once the marketplace will always consult the available inventory on the seller area.

This inventory, therefore, may be the same used by the main store or another one specific and customized for a marketplace or for more than one, with different rules and prices setup.

Setting up a customized inventory means that different terms and prices than all other settings used in the store will be applied. Therefore, you need to set up a new sales policy and a new logistics rule for the marketplace.