"No caminé mucho el domingo pasado."
Translation:I didn't walk much last Sunday.
Same thing..."i didn't walk a lot last sunday" is still marked as incorrect. Reported 12 July 2018.
Duolingo has many variations for its answers, you just need to get one that's in its database. (do not, don't, will not, won't). They also include both English and American e.g. Mum or Mom, shop or store, specialise or specialize, even though they use the US flag to depict the English language.