Well, I think in this example someone else wrote down “buy milk”. Of course I would generally know what that’s likely to mean, and not buy the ridiculous thing. But someone from a culture that’s not used to using milk could easily get confused and buy the wrong thing, to further the example. I guess my point was that it’s never possible to completely unambiguously define when a task is done without assuming some amount of shared knowledge with the person completing the task that lets them figure out what you meant and fill in any gaps