Positions in sequences like arrays are referred to using ordinal numbers (first, second, third, ...). There is no ordinal "zeroth". Ordinal numbers start at 1. This is contrary to cardinal ("how many?") numbers, which start at 0. And talking of "natural" numbers is besides the point. Therefore, referring to the seventh element in a sequence with the name "6" rather than "7" is confusing and provokes off-by-one errors.
Positions in sequences like arrays are referred to using ordinal numbers (first, second, third, ...). There is no ordinal "zeroth". Ordinal numbers start at 1. This is contrary to cardinal ("how many?") numbers, which start at 0. And talking of "natural" numbers is besides the point. Therefore, referring to the seventh element in a sequence with the name "6" rather than "7" is confusing and provokes off-by-one errors.