Seaweed... is a natural source of iodine and it naturally is occurring in seaweed.
Some seaweeds have more than others.
That is why, it is not an 'ingredient' listed per say, in order to make it. Because iodine is intrinsic in seaweed.
Its similar to saying, how much chlorophyll is in lettuce?
Or, what is the quantity of chlorophyll in 1 serving of lettuce.
Chlorophyll is just naturally occurring and intrinsic in lettuce or other vegetables.
I found this:
"Seaweed Iodine levels in seaweed are quite variable, depending primarily on the type of seaweed. Kelp has the highest amount of iodine, with some kelp granules having 8165 mcg/gm. Most Kelp or Kombu has about 2500 mcg/gm. Other common seaweeds are much lower; for example, Nori (16 mcg/gm), Wakame (32 mcg/gm), Dulse (72 mcg/gm), Hijiki (629 mcg/gm). Iodine content is reduced by storage (e.g., in paper bags or open to the air) and cooking. Most of the iodine in seaweed comes in the form of iodide, but it varies depending on the type of seaweed. Absorption of the iodine from seaweed is variable. Seaweed contains lots of stuff besides iodine, some may be useful (e.g., other minerals) and some may be harmful (e.g., goitrogens like bromide and various chemicals like mercury contaminants). Large amounts of seaweed may be problematic."
Table salt also has iodine.
There is naturally occurring Iodine, or added Iodine.