Just take a threshhold dose ( check erowid) should be about 10mg. At the doses 4 aco dmt is active at, there will be no harm done if it is anything else and you will def know if its 4 aco dmt. Even if it was something else, im sure it wouldnt be something that completely awful.
Unless you got it from some sketchy friend or some random dude off the street i wouldnt be too worried. If you bought it off the internet at what looks like a legit site, which most are, its probably what they say it is. If they didnt sell what they said they were selling...there would be no reason for returning customers which= business failll.