It's a salt-free seasoning mix. My store has it in with the spices.
Here's a website that describes what's included in each flavor so if you
can't get it where you are you might be able to find a close substitute.
http://www.mrsdashrecipes.com/products_intro.cfm

If you can't find Mrs. Dash, or want to save a few dollars by preparing
an alternative in bulk, I found this clone recipe somewhere a while back:

1/2 cup crushed dried minced onion flakes
2 tablespoons plus 2 teaspoons crushed dried vegetable flakes
2 tablespoons garlic powder
2 tablespoons dried orange peel
1 tablespoon plus 1 teaspoon black pepper
2 teaspoons dried parsley
1 teaspoon dried basil
1 teaspoon cilantro (coriander)
1 teaspoon cumin
1 teaspoon dried marjoram
1 teaspoon dried mustard
1 teaspoon dried oregano
1 teaspoon dried savory
1 teaspoon dried thyme
1/2 teaspoon celery seed
1/2 teaspoon unsweetened lemonade drink mix
1/4 teaspoon crushed dried rosemary

Combine all ingredients and crush to desired consistency in a food
processor or blender. If stored in a airtight container, the mix keeps
for months.

You can play around with the amounts of the ingredients, or add new
ingredients to create different flavors as well, I personally like to
add a teaspoon or two of crushed cayenne peppers and increase the
cilantro to 2 or 3 teaspoons for a little spicy kick.

While I haven't bothered to calculate the exact carb count for the
prepared mix, Mrs. Dash (original flavor) lists itself as 0 carbs, and I
figure if used sparingly, the carb count should be neglible.

As far as using 1 cap full for a recipe, if you go with a homemade mix
instead, a tablespoon should be about right.

-Rich