Question?

[FlyerChick4]

I'm not entirely sure if this is the right place for this post but it seems like a hear a lot about this in here so what the heck. I am wondering about DJ's chart. I don't fully understand why one would use this because i was looking at it and I know that at the grip heights listed my takeoff is definitely outside the one listed because I am so short (only 5'2"). So I guess my question is what height is that chart based off of cuz not all of us out here are 6 feet tall and my other is why is everyone telling everyone else to use it.