First,
An asset in Stellar is defined by its issuer and its asset code.
Looking at BAT, you can't be sure they mean the same thing without checking with the issuer what their BAT represents.
For ARG, it might just be as simple as someone testing things, and issuing the same asset from three issuers before they got it right.
In summary, the total amount issued for a particular asset on Stellar, is the listed amount.