I read on resveratrol supplements:
What does "standardized to x%" mean in resveratrol supplements?
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It means that whatever the amount of Polygonum cuspidatum Root Extract they used, it contains 50% trans-resveratrol. But that doesn't help you much since they haven't told you how much Polygonum cuspidatum Root Extract is in the blend.
Compare that to
which says the first capsule it is 99% pure, and the total amount of trans-resveratol is 248 mg.