I think was just a minor typo. It refers to the 2020 halving era of 6.25BTC rewards

https://blossom.jumble.social/ca0c1a5d04c48d48a8e2fc0c014415f478e28f08c518082c249c44cfb4c3a11b.jpg

Me too, but looks sexy

69'ing is so 90s. 6.15'ing is for the 21st century! #Bitcoin

I know that folks are saying that it's a halving number with a typo, but I thought there was a goal in earlier btc generations to stack 6.15 bitcoin. It's possible that I'm totally making that up 🤷‍♀️