This article describes the process of importing product quantities in stock for both Narva and French Erply.
Magento reads product stock from French Erply completely automatically according to schedule defined in Erply Module configuration in Magento Admin. It is possible to disable stock updates in configuration if necessary.
Magento reads current stock amount for all products and uses only completely free stock (total in stock minus reserved amounts). Quantities are then compared to the ones on record in Magento and if quantity in Erply is different then product stock is updated in Magento.
It is not possible to read and update stock amounts manually.