Proper way to calculate the amount of sugar in a drink I have recently read an article (in Spanish) about a sugary drink (water-based) with stated the following facts:


Ingredients of the drink: natural mineral water, organic cane sugar, lemon juice made from concentrate (7.9%), ascorbic acid, pectin, natural basil flavoring, natural lemon flavoring and other natural flavorings.
Nutritional values per 100 ml: 18 kcal and 4,1 grams of sugar.


I'm trying to calculate where did that amount of sugar per 100 ml come from. The list of ingredients must be ordered by weight in decreasing order by Spanish law. We do not know the percentage of sugar, but we know it must be at least a 7.9% (the percentage of the following ingredient) of the weight of the product. The nutritional values are calculated per 100 ml, but the density of this drink (as it is not a carbonated drink) must be around 1 kg/l. So asuming that 100 ml of this drink weight approximately 100 grams, in that amount there must be around 7.9 grams of sugar, and not 4.1 grams as the label states (if we do not add the amount of sugar in the lemon juice). Besides, those 7.9 grams of sugar must contain 28 kcal, above the 18 kcal stated.

So given the discrepancy, and assuming good faith on the side of the company that manufactures the drink (and assuming the article copied the values properly from the label), where did I go wrong?
Thanks to all the people who commented in the question post. I wrote a tweet to the manufacturer of the drink and they told me that the ingredient list is wrong because they increased the amount of lemon juice from what was originally planned but did not fix the label, so the sugar should have been after the lemon juice and not before in the ingredient list, hence making the nutritional values compatible with it.

They also told me that the label containing the ingredient list will be fixed in the future.