We need yet another "This has what it says it has" regulation around supplements and vitamins. There's basically no guarantee that any vitamin pill you pull off the shelf has any percentage of it's claimed ingredients. You could be getting 10% of what you wanted, you could be getting 1000% of what you wanted.

Fortunately, the body can handle some pretty wide variation. But unfortunately if you are taking a vitamin because you lack a nutrient, there's really no guarantee that your actually treating that deficiency.