You buy a package of chips which looks like perhaps a single serving and eat the entire bag.  I wonder
what I just ate while I was reading my emails.  (mindless eating another topic for another day)

Wait let me read the label, wow, it was in fact a bag for 2 servings.  It looked small enough for 1.

Always read the labels.  Check the serving size and the number of servings
per package. 

If you eat all the servings you need to multiply everything by the number of servings you
ate.

130 calories for one serving x 2 = 260 calories
380 mg sodium x 2 = 760 mg
2g saturated fat x 2 = 4 g
and so on.

Read those food labels.  You will know what you are putting in your body.