The fully canceled Shopify orders are fetched from NetSuite based on the criteria defined in the NetSuite Saved Search that is present as a drop-down list box (NetSuite Saved Search for syncing order cancellations) under the Settings > Cancellation section and sent to Shopify. Thus, keeping NetSuite and Shopify in sync.
Select the desired 'saved search' from the list. Click 'Refresh' to fetch the latest records from NetSuite. To know more cancellation configurations, go to Sync cancellations between NetSuite and Shopify.