Sorry, I should have been clearer because it's the amount of herb you'd be using in a dose of tea that you can divide by 100, rather than the amount of extract you may have happened to obtained at any one time. If you were to be using, roughly, the suggested amount of 5g of fresh herb in a tea, this equates to 50mg of extract - so your calculation for the amount of extract to start with is correct, [and maybe only some nuances were lost in translation!]
From the linked website:
On a related note, please be sure to make yourself aware of our
attitude rules, particularly regarding discussion of sources. While your extract may be 100% legal, we still prefer to limit discussion of extracts to those which we have prepared ourselves. We are strict on this principle in order to maintain the safety and wellbeing of the site as a whole.