I track my calories in MyFitnessPal and then deduct them from my overall calorie burn from my apple watch. It takes a while to get it right though because your watch adapts to you and how much you burn over time. It also doesn’t update your total calories until the following day. The way that i knew mine were correct is i wrote them out each day on a calendar and wrote out my weekly deficit and looked to see if it corresponded with how much I lost. Now it does, almost perfectly. If I’m in a 500 calorie deficit then I lose 1lb each week. It took about 6 months of wearing my watch and logging lots of different types of workouts to become that accurate.
ETA: the total calories is not the red ring, it’s listed as total the following day when you put your watch on. It adds the red ring to your bmr.