This is not a single brand problem. Iodine supplements based on algae, including kelp algae, naturally vary in iodine content from batch to batch.
The result is influenced by, among others: algae species and age of the thalli, place and depth of collection, season and method of drying. Therefore, it is safest to copy the value from the packaging of a specific supplement.
Sources
- Aakre et al. 2021: Iodine content in seaweed products
- Teas et al. 2004: Variability of iodine in seaweeds
- Bouga & Combet 2015: Seaweed iodine content in UK products