Help with picking a visit time for the Taj Mahal

I’m traveling from abroad to visit the Taj Mahal an I tried booking tickets online to visit the Monument but they ask me what time I wish to visit. I’ll be arriving at Agra at 10 AM so i’ll be going at 11 AM roughly, so if i book Forenoon tickets does that mean I will have to leave the Taj Mahal by afternoon?