This shouldn't be about literal translations, but what would be actually said in the other language. It is possible that this translation is from some book written in the late 19th or early 20th century? Older English written material is not how we speak today, nor would older French written material be spoken the same today. So is the purpose to learn the language of today, or to just translate older material?
I think the purpose is to learn how the language is used in literature as well as causal conversation when meeting someone on the street. Having learned it, there is nothing stopping you from restricting your speech to simple phrases free of cultural context. Older written material is how we speak today. Otherwise we would have to invent an entirely brand new English (or French) language every generation.
Most, if not all, the material used in Duo text taken from copyright free text available elsewhere. You will see identical phrases used as examples in other language courses, for the same reason. I have learned how to ask M. Durant his name in French in three different courses so far. The same question and answer with the exact same use of person
There is only one number (which is five). They are to the number of, i.e. counting up until you get to five. Imagine counting them; ticking them off on fingers or making tally marks. You keep going until you get to five; and think of nombre as "count", so you're counting up until you get to the count of five.
It's literally counting them. That's what we did before we had video cameras and face-recognizing computers to estimate the size of a crowd for us :o)