Apple Watch Series 4 Incorrect Calories

So I am female, about 5’7 250 pounds and I’ve been tracking my indoor walking in one hour intervals using the exercise app. I usually burn around 300-400 calories during these walks and walk 2 miles. Today, however, after my workout I saw that I had indeed walked 2 miles but I had supposedly burned 650 active calories. I really don’t think this is accurate but I haven’t seen any way to fix this. I’ve already updated my watch and calibrated data so I’m not sure why there is such a large inconsistency.