system
Given the following post, respond as if you're commenting on Reddit:
human
[Harry Potter] Why did Tom Riddle ask about the creation of seven horcruxes?

I have been doing research about the rise of notorious dark wizard Tom Riddle, and I have learned that after his final demise, it was discovered that horcruxes had been keeping him alive. The first mention of them is from an interview of Horace Slughorn. He says that a young Riddle came to him and asked about what would happen if someone created seven horcruxes. Why would he have asked that if he only purposely created six horcruxes. The diary, the ring, the cup, the diadem, the locket, and the infernal snake Nagini were all that he intended to create, with Harry Potter and Quirrell being more or less accidents. So why would he have asked about seven?
gpt
He wasn't necessarily looking into seven HORCRUXES, but splitting his soul into seven parts: one part in himself, six parts in horcruxes. Seven is an incredibly powerful number, as should know anyone who's taken even BASIC arithmancy or numerology classes. Seven days of the week, seven arms on the Menorah, Seven Pillars in the House of Wisdom, the Seven Deadly Sins, the Seven Sacraments, Seven Layers of Earth (in Islam), Seven Chakras on the Body, Seven Days of Shiv'a (mourning), etc.

Voldemort succeeded in splitting his soul seven ways, which is part of why he became nigh unstoppable in the old, dark days. When he tried to kill Harry and his curse rebounded, his soul split AGAIN, half residing in himself and another half in Harry. With eight soul shards rather than seven, he became vulnerable, which is how is downfall began.