Another analogy. Will you take the train or the ferry to Manhattan tomorrow? You don’t know (yet) and neither do I. But it is surely only one of them, and we will both (if I stalk you) know tomorrow.
Let’s say you pick the ferry (good choice!).
Even today it is true that you are going to pick the ferry. We can’t know this, but it is the fact. However, it is a truth about your choice. Your choice is forever, in that sense.
This is essential to understanding why being above time makes a difference. When someone hears that Hashem is above time, he can say, “Well I’m not, and if He knows what I’ll do then it’s decided already.” Therefore, the above is a first step to understand this.