I thought it most likely A. discobola because of the larger brownish blob two thirds along towards the forewing hindmargin and the distinctive curve downwards of the broad black streak on the forewing below the thorax and towards the base of the forewing. However, looking at both species on the ALA again its very diffucult to tell them apart., and anyway I'm not sure the ALA can be relied on to be always definitive. Moths in the ACT'does not mention either species. Comparing the two species on iNaturalist, A. leptosmela seems to always lack any brown colouration at all, whereas most A. discobola have a distinct brown blob as I described.