Maybe they're just measuring lines committed (total guess)? If you count white space, comments, variable and function declarations, and boiler plate code like

Maybe they're just measuring lines committed (total guess)? If you count white space, comments, variable and function declarations, and boiler plate code like creating loops, then maybe I could see how they got there. Kind of related, but if I think about autocomplete, it probably writes about 10%-20% of the individual characters in my code. While it is totally misleading, it wouldn't be factually incorrect to say that autocomplete writes X percentage of my code. I wouldn't be surprised if GitHub is using some "misleading, but technically true" metric for this.