That's not quite what it says. Essentially, as long as he is 18 (or a young 19), the ELC will be extended one year. It's automatic. The only thing that is subject to change is things like Paragraph 1 salary, games played bonuses, etc. So they could change some of the terms of the contract. But that one year extension is not something either party can refuse.
Casey is 19 and has a November birthday, so if he signs his ELC this year and only plays one game then it burns a year.