I had a family member go through this. Proof of travel, photos of trips, phone bills, so many phone bills, etc.

But I can easily see how it'd go wrong. If you spend your visits impersonating rabbits, what proof do you have? If you spend more time on snapchat than the phone, what proof do you have?

There's an old trope of "yes, I do have a girlfriend. you wouldn't know her, she's from another school." She lives in another city, she's from Canada, etc. How do you expect your friend to prove their claim? Now replace the playground with INS/USCIS.

It ends up being a very vague question because there's no set limit of what level of evidence you need to reach, you just need to "satisfy" whoever opens that file.