Reset effected calories

I have reset my watch using the privacy and reset function but it’s dramatically effected the calories I’ve burned in my work out. Done a class this morning normally I burn 3-400 calories this morning I burned 115- for the first 30 mins i was only burning 2 calories a min!! I was dripping and my heart rate was where it normally is around 130. A walk round the park burned more apparently this afterNoon!! Going for a run and I’m dreading looking at what it’s going to say. Any help will be appreciated x