Calories don’t match up in app

I went for a walk today, and in the activity it says I’ve burned 483 calories. The step count for today says 1313 calories, and the calories in/out says 391 calories (active). Oh, and on the calories widget on the watch it says 1360. 

Activity:

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Step count:

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Calories in/out:

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Shouldn’t they match up a lot more than this?? And how on earth is the step count calories so extremely high when it only says 483 calories for the activity?? That walk is the only activity I’ve done today, otherwise I’ve just been sleeping and moving around in my flat. And how is it only 391 for the calories in/out, when it clearly says 483 calories for that walk??
Does someone understand this? Is this caused by a problem with Garmin Connect? Is it me who has misunderstood something? 

Oh, and I have an iphone ios 13.1.2 if that helps. 

Thank you for any help!