A count is only useful if the camera can see the rep. The place that works is the floor, not a chair and not your hand.
In front of you, tilted up
Set the phone down so the lens looks back at you. Prop it on a book if the floor is too flat. You want your whole body in the frame: head, hands, hips, feet.
Wait for the lock
Jym draws a skeleton. It stays dull until it has you, then it turns green. Start the set after that. If you begin early, those first reps are easy to miss.
Light and space
Face a window if the room is dim. Stand far enough back that your head does not leave the frame at the top of the rep. The same spot, every time, makes the log easier to trust.