Amazon DynamoDB Import from S3 now supports up to 50,000 Amazon S3 objects in a single bulk import. With the increased default service quota for import from S3, customers who need to bulk import a large number of Amazon S3 objects, can now run a single import to ingest up to 50,000 S3 objects, removing the need to consolidate S3 objects prior to running a bulk import.
Source:: Amazon AWS