Data Stream Backfill Still Processing
It's possible that the Replication API (Backfill Processing) is still going through the data changes and writing those changes to the Marketing Cloud databases that store these Synchronized Data Extensions and all associated field data. This synchronization backfill process relies on the API Communication from the Marketing Cloud to the Sales Cloud, as well as the number of fields and rows specified. Keeping this information in mind, please estimate 500,000 to 1,000,000 rows per hour.
Data Stream Backfill Processing Issues
If you've already given the system an appropriate amount of time to complete the updates and you still don't see the expected data changes, it's possible that the changes didn't propagate as expected across all necessary database tables. In this instance, a Support ticket will need to be opened with Marketing Cloud Support to help identify and correct the issue.