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This article about trans fat content in foods http://www.nytimes.com/aponline/us/AP-Diet-Trans-Fat-Labels.html brings up an important point: the info on the nutrition facts label is based on one serving.

That one serving is also listed on the label. Sometimes a package may contain two servings, even though we routinely eat the whole thing. For example, I ate a Udon noodle bowl for lunch today, and even though it came in one cereal-size bowl, the label says it serves two. I ate it all (I was hungry!)

Legally, food companies are allowed to round the numbers on the nutrition label. So if a food contains .4g of trans fat, it's allowed to state "zero grams trans fat" on the label. If you eat two servings, you get .8 grams trans fat, but there's no way for the consumer to know this.

You have one important recourse: read the list of ingredients. Anything that contains partially hydrogenated oil is going to contain some amount of trans fats. Avoid these foods as much as possible.

And of course, just eat one serving of everything else (unless it's fresh fruit or veggies)!