"7.62" could be any number of .30 caliber rounds. While you are "technically" correct that there are various 9mm rounds out there, most of the time people NOT referring to 9x19, 9mm "Luger" or 9mm Parabellum will specifically state as much aka 9mm MAKAROV or 9mm Winchester magnum. With rifle rounds, there are at 3 quite popular military cartridges that nclude "7.62" in their name, and few people use the "7.62" designation alone, to avoid confusion. Basically...what you were told elsewhere is right...9mm, to the vast majority of shooters, will be recognized as 9x19, but a "7.62" round would liekly cause some confusion in name alone(*LOOKING* at the 7.62x54, the 7.62x39, and the 7.62x51, its quite easy to distinguish them if you are familiar with the rounds)