A gram of dietary fiber has about 2 calories, rather than 4. So you can correct the total number of calories by multiplying the grams of fiber by 2 and then subtracting from 4*carbs.
For instance, if your 32g of carbs were straight sugars, that'd be about 32*4 = 128 calories of carbs. But, if there are 26 grams of fiber in there, then there are 26*2 = 52 fewer calories. So that's actually only 128 - 52 = 76 grams of carbs.
As far as the whole "don't count" thing, that's really aimed at diabetics, who have to care about that sort of thing more than other people do. It's not total bs, but the whole idea that those grams just "don't count" is a bit of an exaggeration.