Review Default Mappings
To ensure that the data flow is consistent with your business needs, you need check that the synced record has the accurate data. After doing a test sync or manual posting, compare the source record with the synced record to confirm that the mapped fields were synced. If you need to modify or add mappings, contact NetSuite Customer Support.
When a link has been established between a NetSuite record and Salesforce object, the synchronization of any updates done to the data is two-way. Any field updated on NetSuite record will sync all mapped fields mapped for this data flow from NetSuite to Salesforce. The sync also applies to data flow from Salesforce to NetSuite.
You need to ensure that only the fields that are expected to be synced to the other system are defined in mappings. This can be observed and verified during subsequent updates on existing records that are linked during Historical data sync.