Why can equal amounts of a nutrient have different daily value percentages?

I don't totally understand the daily value system, but I was looking at some food wrappers and found that in different products the same amount (number of grams) of a nutrient might equal different daily value percentages. For example, in two different products there were 2 grams of dietary fiber each. One package claimed that this was 8% DV and the other claimed it was 6% DV. Please clear my confusion!