Factors that affect preparation strength
Using fresh herbs versus dried herbs
Using cultivated/farmed herbs versus wildcrafted herbs
The menstruum being used: water, vinegar, alcohol, oil, honey, etc.
The preparation method used: folk verses ratio tincturing, cold infusions versus heat infusions, etc.
Length of maceration time (how long the herbs set in the menstruum)
The point is this. It’s very difficult to put a specific dosage on herbs due to the fact that there are so many variants in the preparations. Store-bought preparations also tend to be more standardized than homemade preparations since herbal manufacturers have their processes down to a science and the batches are consistent time and time again.