Tracked activity calories are 250 calories higher than non tracked for the same workout

[Adamcar]

I do megaformer pilates, when I track my workout, I classify it under weights and a 50 minute class will yield me 350 to 400 calories. When I forget to track, I only burn 100 to 150 calories over that span. Why is there such a divergence? Makes me distrust the activity tracked amount as inflated.