The Mets half of the equation affects both games. If the Mets win, it affects both outcomes. If the Mets lose, it affects both outcomes. It is not an independent variable. The Mets effort to stay ahead of one directly impacts their effort to stay ahead of the other. I might have a 50% chance of marrying in my lifetime and a 40% chance of having one or more children, but that does not compound to a mere 20% chance of marrying and having children, because each act directly affects the other.