Well it means that that all the footage is on the table and they are in the editing phase. That's the simplest way to describe it since post production has many stages. During which the director can change his mind about a piece of the movie and in this case they didn't like how the Supra sounded in this race scene. So they went out and recorded a bunch of cars to see which one they liked the best.
I don't know if you'll see my name in the credits yet. Its just the sound of the car they will use so its not as big of a thing as using the whole car in the movie. In any case I'm in it for the fun since I get to drive it myself. They pay a small amount, probably enough to buy one tire, LOL.