This says it’s 200 calories/100 grams:
https://www.aqua-calc.com/calculate/food-weight-to-volume/substance/tajin-coma-and-blank-clasico-blank-seasoning-coma-and-blank-lime-coma-and-blank-upc-column--blank-633148100013
That’s about 2 calories per gram, or (if it’s all carbs) 0.5 grams carbs/gram product. 1/4 tsp is 1 gram. So, if you ate 2 tsp, you would get 2 tsp x (1 gram product/ 1/4 tsp) = 8 grams product, about 4 g carbs. So, a bit high if you care about that amount of carbs and you eat that much of it.
Though I’m not sure these numbers add up. If the dehydrated lime juice is 0.5% of the weight, it seems like that can’t be 0.5 grams carbs per gram product. The chili peppers (main ingredient) could have some carbs, but how “accessible” are those?
If anything, I think there’s a possibility that making meat more palatable by using this spice could mean you eat more. Is that true? Not sure. That would be a hard study to design.