What's the maximum dosage of passion flower extract in mgs before it's too much?

Nobody truly knows: Benefits, dangers, and side effects are uncertain unless the extract is a real medicine approved for use by the FDA. Otherwise, claims may be just claims, and nobody knows for sure. Also, one cannot be certain what actually is in the container, what the concentrations of the substances are, where they came from, what the purity is, what the differences among batches are, etc... It's all uncertain.