Carbs vs. Net Carbs

So I am new to whole low carb diet - following the guidelines of the Atkins diet.

For the past two weeks I have been counting only my carb intake, not my net carbs.
Does this mean I have actually been eating less than I'm allowed!?

This is my idea of working out net carbs

Total carbs minus fiber = net carbs.

E.g.

Old El Paso Hard Taco Shell
1 Shell
7 grams of carbs - 1 g of fibre = 6 net carbs.

Is this correct?