I wish I knew. Personally, I use counter attack only when playing defensive. Which happens maybe one time per season. I try to imagine what makes sense. But in the end, this is a game engine that runs on mathematical calculations, not on sense. Offside trap might work like: -10% chance to create a goal chance, but when creating one +5% to score from it. If I programmed it. As I did not, it might work like whatever. Sorry, I really don´t know.