Apple Watch activity is off

Sounds like you didn’t start a workout. Apple Watch uses “workouts,” each with its own algorithm, to estimate calories burned. Since a 160bpm run vs 160bpm bike ride burn different amounts of calories, we have to choose what workout we’re doing. It’s also why there is such a long (but incomplete) list of workouts. Each one calculates calories burned differently. The watch appears to refuse to guess for anything other than walking, running, and stairs, which probably have really unique patterns on the accelerometer that senses motion. Walking too slowly will not trigger it though, some elderly folks have not seen it record without them starting a workout.

Are you recording this as a workout and if so which one?.

You need to do it as a workout for it to measure properly.