Maybe I'm overthinking the golden ratio but it seems kind of ridiculous to not text back until she texts twice or calls twice. I understand you want the girl to chase you but is she really going to keep double texting if you don't text back? Especially if you're trying to schedule a hangout.
Quit thinking about yourself on a ?/10 scale. You're not a woman, you're a man. Women don't rate men on a 10 point scale. Its either yes or no to them and there will always be someone that will say yes.