To use a dosage makes an herb more than just a herb, it then becomes a medicine and you know who has power over all medicines, the FDA. There really should be NO NAME on all herbal bottles, because again the name can make it a medicine. Even books that explains herbal dosages make the herb a medicine, so all herb stores and all people who sale herbs basically have a problem in the USA and many countries.
I normally make a Dr. Christopher type herbal formula or Dr. Clark and allow their books to describe the suggested dosages. Most are 2 capsules 3X a day or 1 tsp. 3X per day in general. I prefer to just take as the body wants and when you don't think about the herb, then that day you don't need it. If you know what a herbal formula does and you want to make the body expell mucus for example, then you would want to take what is needed and books explains these many things.