"I read the books at 9:00."
Translation:Heluhelu au i nā puke i ka hola ʻeiwa.
I'm not one of the "Duolingo people", just another student of Hawaiian, but I'll try to answer.
The particle "i" has many roles in Hawaiian. In this sentence alone, it has two roles: in "i nā puke" it marks "nā puke" as the direct object of the verb "heluhelu". In "i ka hōla ‘eiwa", it indicates a location in time.