huh...

Soup, stock, chicken, home-prepared = 8.7g carbs

Water, chicken, carrots, celery, bay leaves, spices, salt. All boiled and strained into a nice golden liquid.

Can it really have 8.7 carbs per cup?

The one carrot I put in only has 5.8 grams and the 2 celery stalks add up to 2.4 grams. That would total 8.2g if eaten. But boiled in a soup and strained, would all the carbs be retained in the broth alone?

IMHO, it's quite possible that the sugar carbs contained in the carrot might have cooked into the broth, but a lot of the carbs in the celery come from fiber, which you removed when you strained the broth. As I say, JMHO.

Did you enter this recipe into My P.L.A.N.? If so, it should give you a count for total fiber, as well as total carbs. You could subtract the fiber from the carbs to get the net carbs, as is usually done.