When withdrawling money from my bank account, should I look at the posted balance or the available balance?

They are both different. As of now my available balance is higher due to a deposit I made earlier in the day. If I were to withdrawl money what should I be looking at? Posted balance or available balance? I don't want any fees for withdrawling more than what I should.|||Available balance===it is a real time balance, meaning the money ready for you to use it