The article only reports number of microplastics without reporting mass. This is particularly difficult to interpret when fibers are responsible for so much of the total:

Notably, across all samples, nearly half (44%) of the identified microplastics were fibers, which is consistent with other studies suggesting that fibers are the most prevalent form of microplastic in the environment.

Are 4 fibers of 50 micron length 4 times more dangerous than one 200 micron long fiber? There's no discussion of it in the article, but reporting microplastics by number of countable particles carries that implication.