GitHub Readme Stats

Hello Anurag,
Firstly I'd like to appreciate you for your wonderful service, the GitHub Readme Stats. I use it and I am grateful for it.

I have a doubt though. What does it take to go from one GitHub rank level (C+) to the next higher one? 

Please shed light on it. Please excuse me if I asked this in the wrong place (I'm new to GH!).

Thanking you,

Yours Sincerely,

Sushant Nair.