Should be percent calories.
I don't even trust my own memory without proofs, so below is my support as I'm not aware of a formal authority that codifies that (though there probably is one, but conventions could vary between countries).
1000 g of fat is 9000 calories.
100 g of fat is 900 calories.
100 g of carbs is 400 calories
100 g of protein is 400 calories
Labels brake things dow by calories from X, not weight of X (though I guess one could calculate weight from calories, but why add a needless step).
It makes more sense for a percentage to be in calories and that is the only way I have seen it done.
If 50% fat by weight, then 69% of all calories would be coming from fat. This is high even by Keto standards and while possible, does not make sense in most contexts.
Here is an example from standard usage.
"A ketogenic diet primarily consists of high fats, moderate proteins, and very low carbohydrates. The dietary macronutrients are divided into approximately 55% to 60% fat, 30% to 35% protein, and 5% to 10% carbohydrates. Specifically, in a 2000 kcal per day diet, carbohydrates amount up to 20 to 50 g per day."
50x4=200 which is 10% of 2000.
