harry potter - Could there be an eighth Horcrux?

Since the magical number is seven for Horcruxes, and Voldemort made Harry unintentionally then there must be an eighth right...???

1. Diary


2. Ring



3. Cup


4. Locket


5. Diadem


6. Nagini


7. Harry (Does not count because Voldemort did not know that Harry was a Horcrux)


8. ??????