I was curious and did a search. There appears to be a bit of speculation as to what that means. But I found this article -
Elon Musk ordered Tesla engineers to stop doing a critical brake test on Model 3s and the quotes from Tesla seem to me to indicate it simply means the vehicle is done, including any repair, and "out of the gate".
The employee Business Insider spoke with said the factory-gate distinction is important. They said it means the company most likely reached its goal by finishing cars that had already been through the production line the previous week but were held back for rework, then readying them for factory gating.
Arnold disputed that notion, saying Tesla has been consistent in how it reports its numbers.
He said: "A small number of cars are built during a week but factory-gated the following week, just as a small number of cars built the prior week may not be factory-gated until the following week. Both of those points are true for this last week of production, just as it is true every week. We are reporting our production numbers the same way as we always have."