"after seven months of school he finally counts up to ten" .. tahle možnost?
Já bych řekl že ano.
"After seven months IN school, he is finally counting to ten." Think you can use IN as well as OF in this sentence.
I agree with albeck's interpretation with finally at the beinning of the clause. It seems more natural in English. It should at least be accepted. The duolingo answer seems unnatural and stiff although in general usage.
What is wrong with "after seven months at school..."