Pass the Almonds, They Just Got 20% Lighter
The same is true for some other nuts, seeds, and vegetables.
The old school method for determining calories was pretty simple. Put a controlled amount of a food in a chamber, set it on fire, and measure how much heat it put out. After measuring thousands of foods all the data was put into tables. Over a hundred years later, and we still use these same tables today to determine total calories in a food.
So in the lab a handful of almonds might be able to supply around 421 calories. But your body burns food differently and you may only be able to use 336 of the calories in that same handful of nuts.