How does it work?

A fruit package with one bad apple, or a bad package, is represented with [2,0] or [0,2]

A fruit package with two bad apples, or a rotten package, is represented with [0,0]

What do they mean by this?

But they are not booleans

This is what I wanted to do but I was puting the recursive function at end which mas making the result string inverted
Nice one!