What happens if you accidentally insert data into a replication target table?
Delete the rows to not cause any conflicts later. If you still need the data insert them on the publisher after you deleted them on the subscriber.

You do not need to worry about the identity seed. Replication inserts its own values and does not rely on the identity-auto-value-generation. As this is a table on the subscriber you should not insert data ever again, so to you it should not matter what the identity seed is either.