I'm not surprised by this report at all. There have been a couple studies conducted and it has been found that anywhere between 25%-45% (depending upon the study) of supplements you find do not have in the bottle what is advertised on the label. Furthermore, there have been times when dangerous substances have been found, or dangerous levels of certain ingredients such as iron.
I have a book called "the comparative guide to nutritional supplements" which rated over 500 supplements. Centrum rated extremely low: a 5.2%. Gnc rated higher at 46.9%. However, if you want to be sure that what you are taking has what is promised, ensure that is will dissolve in your body the way it is supposed to, and get the desired effects you are looking for, then you must look into a supplement that is pharmaceutical grade vs. Fda approved. Having a pharmaceutical grade supplement guarantees that what is on the label is in the bottle and it must pass rigorous tests before being released.
The products I sell are pharmaceutical grade and were actually rated #1 in the comparative guide, coming in at a 96.1%. Drop me an email and i'd be happy sending out free information to anyone, or visit my website by clicking on my name to the left and following the link.