If you scroll lower down, there's a table with the amounts from the different samples from different fires.

I think it's telling that the amounts in the Palisades fire are by far the highest. That fire had a huge number of structures burned, so the samples of suppressant scraped off of leaves and things is going to be mixed with smoke and ash particles from those burning structures. It doesn't make sense that the amount of heavy metals would vary wildly from one batch of suppressant to another, but it makes perfect sense that the amount in a field sample would vary depending on what's burning in the area.