are unadorned brackets always "concentration"?

I thought that if there are unadorned square brackets (i.e., no sub or
superscripts), then that means "concentration of...". However, on this
wikipedia page
<https://en.wikipedia.org/wiki/Salt_metathesis_reaction#Counterion_exchange>,
there are lots of examples of unadorned brackets. My knowledge of chemistry
is limited, but to my eyes, these uses of brackets are not meant to be
"concentration".

Are they just grouping symbols to indicate the counterion? If so, how do I
distinguish between their use as grouping symbols and their use as
concentration?

Thanks,

    Neil