I've gotten into the habit of specifying whether my Natural numbers are starting at 1 or 0, because about half of my lecturers assume 0 and half assume 1 (note I'm in the UK, so they're all researchers & doctorates, and some are professors - so if there was some universal standard, they'd almost certainly be applying it). Most of them also point out, standards vary, with generally only the incompetent ones assuming it must be 0 or 1 and marking you down for using the other.