He always wanted to create 6 (to split his soul into 7).
Before killing Harry's parents at Godric's hollow, he had created 5 (diary, ring, locket, cup, diadem). Harry was the 6th, but Volde didn't know that.
So after his remaining soul fragment went from body to body, in 1994 he was made a homunculus by Pettigrew (rudimentary body like a baby). After in that baby form, the same year, he found Nagini and made her a horcrux. He thought it was the 6th, when actually it was the 7th. Finally splitting his soul into 8.
In conclusion, he always intended to make 6, always thought he made 6. Voldemort never realised he had made 7.