If this was the first question, and both incomes are equally common, then before they asked your income they would estimate your chances of siding with the plaintiff as 62%. They ask the question, and either your chances go up to 75% or down to 50%.
If one of two answers gives "no effect" then so must the other.
Think about it like point system. Based on the answer, the plaintiff gives you a point and the defense gives you minus a point; or nobody gives you any points. Theoretically, maybe you should have started with half a defense point, but I don't think that's how it's really run.
If one of two answers gives "no effect" then so must the other.