What's Behind the Numbers in '9'?

http://scifiwire.com wanted to know the meaning behind the numbering in Tim Burton produced 9, this is what director Shane Acker said:
"I was just having fun and kind of exploring this idea that these numbers would be versions in some way," Acker said in an exclusive interview last week in Beverly Hills, Calif. "As the numbers get higher, the sophistication of the creatures gets more complex and more refined. So when 9 comes along, he is the last version, the most up-to-date version, the most complete, who has a larger, more holistic view. We just bought into that conceit, and then we tried to have as much fun with that as we could. What does the number 6 mean? What kind of emotions does that elicit, that number? What could this character be? So we tried to separate them all, as they all have their own strengths and their own weaknesses, and together they're able to complete themselves, and they become a whole once they finally get working together."

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