I feel this example shows one of the weaknesses of the learning model. Seems like "even" is the only idiomatic translation here, but a non-native speaker can only guess which of the provided translations of "até" is correct. I haven't thought of a better way yet... but it feels unfair somehow to get this wrong when there's no earlier hint about the idiom.
And to reply to myself -- if you encounter this sentence first in the multichoice question where you're asked to pick a translation, you can infer the correct meaning of até in this context. If you encounter this sentence first in any other context, you can only guess. So it seems to me that there are some words/idioms that should only be presented in certain ways first so the learner has a chance of inferring meaning corrrectly, before they see the word/idiom in a more ambiguous context.
From what I found out so far in Duolingo, if a word has different translations, the most appropriate translation for that expression is usually the first one on the list. It is the case here: "even" is listed before "until". Furthermore, Duolingo's method of learning is much of a trial and error method. Error makes you practice more and better memorize and/or understand the words and phrases. So, in a way, making you fail is part of the process. (note: this is my opinion, not a Duolingo fact).