The walk workout only counts if you walk over a certain speed. No idea what the speed is. I suspect it varies based on the information you enter about your height, weight, etc. I typically walk between 3.5 and 4 miles per hour and most of it counts. Walking will count towards the ring even if you don’t start an actual workout, if you walk briskly enough; but it won’t show up in the activity app unless it is an actual workout.