Before you collect a booty box, what you get from it isn't stored in it per say, so, before you click on the booty box it is "empty". When you click it, a countdown is initiated, and in this time, what you get from it is randomly generated, and that's why there is a slight delay after the countdown is finished to the time when you receive what was generated.
This is why any LF4 locating scripts are bullshit, and keyloggers.
Sorry if the explanation doesn't make sense, it's a bit hard to explain fully.