RDA (Recommended Dietary Allowance)
The average daily intake level of a nutrient sufficient to meet the requirements of nearly all (97-98%) healthy people in a given life stage and sex group, set by the National Academy of Medicine. It's a target for adequacy, not a safety ceiling -- that's what the Tolerable Upper Intake Level is for.
Example
Magnesium's RDA for adults 31 and older is 420mg (men) / 320mg (women); it is 400mg / 310mg at ages 19-30. 94.7% of on-market magnesium products declare less than 420mg (the adult male RDA) in a single serving.