Erplain allows you to send your orders in separate shipments. They are partial shipments, it can either be because some products aren't back in stock yet or because a buyer wants a staggered delivery for their order. For this, you will start by creating a sales order:
Once the sales order has been created, you can create a shipping order. For a partial shipment, you will just need to edit the quantities for any product in the document, which will adjust the on-hand stock in real time accordingly. You can also leave a product out of the shipping order by unchecking it, which allows you to ship that product at a later date.
This gives you a shipping order with the quantities you entered for each product.
If you go back to the sales order, you will see how many products are included in your shipping orders and how many are still awaiting shipment.
By creating a new shipping order, the values are automatically adjusted based on the quantities remaining. You can create as many shipping orders as necessary until the order has been delivered in its entirety.