I don't have a return that has had AFR done to look at, but the only box that's there says "The CRA Indicates that you have not filed a return for the following years" and the box only takes 4 numbers. So I'm guessing that if anything, it will show a year that you have not filed for.
It might just be something the development team uses for debugging or testing, like the weird box at the bottom of the NETFILE form.
