Inventory is synced for any product that is linked with a remote service. That is, any product that was exported from Intrakr or imported into Intrakr from the remote service.
Quantities are deducted from Intrakr as orders go through in the remote service. Orders are synchronized a few times an hour (typically within 20 minutes). So, if a customer purchases 5 Widgets, 5 will be deducted from that Widget in Intrakr within 20 minutes or so.
When a product's quantity is changed in Intrakr, that quantity change is reflected in the remote service immediately. Note that the change is reconciled, not the hard number. For example, if an Intrakr product quantity went from 10 to 15, the quantity of the product in the remote service will be increased by 5.
Any manual changes to inventory in the remote service does not take effect in Intrakr. This allows you to manually correct any discrepancies or to store a different quantity for a product in your storefront, if you choose.