Why was Booth admitted into the presidential box?

[Anita]

Terry's theory makes sense if one can definitively place Forbes outside the box when Booth handed him the card. Forbes himself claimed he was inside the box when Booth entered. " I accompanied [Lincoln] in the carriage, was with him from the carriage to the box in the theatre, and was in the box when the assassin fired his fatal shot. (FORBES) http://chicagohistory.org/wetwithblood/b.../index.htm

Does Terry address this?