Translation:Two hundred thirty-four is not a digit, but it is a number with three digits.
234 ne estas cifero, sed estas nombro kun tri ciferoj.
is rejected. But in at least one case I’m aware of in this course (with a much larger number), writing the number out in words is rejected and only the numeric form is allowed.
Is there a bright line where one should do one or the other (I was imagining so, with three-digit exact numbers being the line, but maybe it’s four?), or should I report my answer as correct?
I don't make the rules, I just observe them.
Cool, but by “why?”, I wasn’t meaning to ask the intentions behind the Duolingo design choices. Rather, you seem sure, so I meant “why and how do you know this?” If they’re written down somewhere, I may have simply missed them and would appreciate a link.
I asked myself the same thing. The difference between 'kun' and 'per' was said to be "kun" = "together with some(one/thing)" and "per" = "by means of / using" Applying this to "nombro kun tri ciferoj" makes me raise an eyebrow. The word "kun" seems very english-thinky, and I first wanted to replace it with something else. Maybe a word indicating contents, like "da", or a word for its ingredients, like "el". The same way we have "Ĝi estas taso da teo." or "La skribilio estas el plastiko." Why is "kun" okay?