You're making sense, but you've misunderstood. The idea is that before you even come to your logical (or illogical) conclusions and come to a decision, that decision was already made for you. You would never have made a different decision. The decision was predetermined. You being you, you would always make the same decision.

Thats where determinism comes from - everything is already determined, there's a set path. Being unable to deviate from that set path is what people mean when they say that free will doesn't exist.