It’s usually used in the context of a restaurant kitchen. Like if they run out of olives they would yell eighty-six olives. So don’t sell anything with olives without warning and don’t go looking for them.
To add, that’s the only context I’ve ever heard it used in when working in restaurants (to convey that we can’t sell or offer anymore of a thing). If someone order a lasagna with no olives, no one will say “lasagna, 86 olives”.