On the BM54 (Euro version) there are two sets for each wave band, i.e. AM/AMA, FM/FMA, LW/LWA etc. You toggle between them by pressing the AM/FM buttons again.

When on AM you get a list of presets, when on AMA you don't. It's the same for FM and FMA, but with RDS on FMA you get a list of all recievable stations, not quite sure what AMA is all about, maybe they thought RDS may come to AM?