YOU SAID:

my aunt had eaten ten thousand big macs

INTO JAPANESE

私の叔母は1万台のビッグマックを食べていました

BACK INTO ENGLISH

My aunt was eating 10,000 big macs

INTO JAPANESE

私の叔母は10,000個のビッグマックを食べていました

BACK INTO ENGLISH

My aunt was eating 10,000 big macs