Java what does a protected variable mean in enum type?

In Java 9, I can write code like this:

enum Abc {
    A, B, C;
    static protected int foo = 4; // what is the purpose of the protected variables like this in enum?
}

I think it makes no sense, because we cannot inherit or implement an enum.

Edit: This question is the same with Why are protected members allowed in final java classes?

Answer

It means just what it always means: accessible only from subclasses or classes in the same package. You're right that since you can't inherit the class, it's not any different from a package-private field in practice.