Where Does Carb In All Meat Cat Food Come From?

Hello!
I am calculating cat food carb content. But I wonder, when there's no carb food listed in the ingredients, where does carb content come from?
For example MAC's Duck, Turkey & Chicken ingredients are:
Meat (min. 20% duck, min. 25% turkey, min. 25% chicken) and animal-by-products (duck heart, duck liver, duck lung, turkey heart, turkey stomach, chicken heart, chicken liver, chicken stomach), minerals
Analytic constituents, are:
protein 10.4 %
fat 5.8 %
fibre 0.5 %
ash 2.5 %
moisture 79.0 %
Which means there is 1,8% carb content in wet basis and 8,57% carb content in dry basis. But what ingredient does this come from? When all ingredients are meat and animal by-products and there's no vegteble or fruit or grain listed?

Sounds like liver and other byproducts have carbs. 44 Healthy Low-Carb Foods That Taste Incredible

Byproduct especially stomach and gizzards could contain plant matter don't forget poultry do eat grains so remnants of that may be found in the organs.

I agree with all of the above commenters' suggestions since any of those things could play a role, but I also want to point this out:

(min. 20% duck, min. 25% turkey, min. 25% chicken)

The figures for this food (which I think I found on a pet food site) are mostly likely the guaranteed analysis, based on data that are a little flexible, hence the "minimum" figures for each meat. That means that any calculations you make with those figures could/will be a little off. (And individual batches could vary slightly, too.) Which is why it's always best to write to the manufacturer if you want more specific data like actual ("as fed") carb figures.

Another thing to keep in mind is that some of the thickeners that are used in certain foods (apparently not this one, however, if it's not listed) may raise carbs to varying degrees.

Probably whatever the animals ate in the wild

It is weard, isn't it? Just to note, it's not only about a specific brand or taste! It was only an example! I was just researching wet food content and calculating carbs, and wondering... Mabe it is reasonable that some meats and organs contain carbs though!