Perhaps when you finish high school you will have learned some basic probability so you won't be amazed at such events.
Well, the problem with your figures is that you are assuming a randomly selected jury. That is not how it works, although your figures are perhaps representative of the pool of potential jurors. The defense and state lawyers have some flexibility to reject potential jurors that they feel would be biased. The state in this case would have wanted to reject white or hispanic men while the defense would probably want to reject blacks. Given those strategies, the likelihood of eliminating all blacks from sample of Florida's population if fairly high. I bet you could eliminate blacks form the jury in 90% or more of that state's trials if a lawyer was so inclined. Perhaps you should finish university and get some real life experience applying statistics in real life circumstances before you shoot off about your mastery of a subject.