The max dose per herb is what is at the upper range in your monograph. Many of the herbs on this course are pretty safe herbs though so if you go over a bit, then the person taking it is likely to be okay. The dose range in the monographs is the effective and safe range though so it is best to stick to that and it is incredibly important if working with strong or toxic herbs (which are not included in this course).
Correct the max dose of dandelion leaf tincture 1:3 is 18 mL/day.
And yes if you are doubling up on herbs but in different format, you’ll have to do some math to work out what is a safe and effective dose. Here’s a quick example for you, say you want to give someone dandelion root and the dose range is 1.5 mL- 6mL/day of a 1:3, that can be figured out to be equivalent to 0.5 g-2g/ day. If you wanted to do tincture and capsules you could safely do 4 mL of tincture and 1 capsule (equalling 0.5g) of dandelion root per day safely.
It is often easier and just as effective to include a herb in just one format.