On the older Athena, the sediment cartridge was listed for the left-side first filter position and BioStone Plus for the right-side second position. Those details describe the older product family; they do not mean an H2 cartridge fits an Athena JS-205. Verify the name and model printed on your machine.
The Athena 7 H2 is a different ionizer, not a cartridge substitution for the old JS-205. Compare it with Athena 9 H2 and Delphi H2 according to your preferred countertop or undersink installation, and ask AlkaViva to confirm the right next step for your setup.
H2 Series replacement filters are designed for H2 Series machines. Do not order one for an older ionizer without checking compatibility with AlkaViva.