Must be a weird optical illusion but it looks to me like you’re holding the norns with one hand, then holding the phone with another hand, and then using your third hand to push the side/volume button on the phone to take the actual photo.
(which reminds me of my favorite passage from 50 Shades of Grey:)
Christian Grey put his thumb in my mouth. And then the other one. And then two more. ”Wider,” he said as he put in one more. “I bet you’ve never had this many thumbs in your mouth.” I hadn’t.