I wouldn't be surprised if "up to 20,000" just means Jaguar said they can't build more than that because it would interrupt their ability to meet their regular

I wouldn't be surprised if "up to 20,000" just means Jaguar said they can't build more than that because it would interrupt their ability to meet their regular orders and/or it would require too much investment / hiring to expand their factories. Although, if 10,000 were definitely enough, they might not have made an agreement for 20,000, so maybe it does sort of tell you something.