And 63% approve of sex outside of marriage? How can 67% approve of an unmarried woman having a baby but only 63% approve of sex outside marriage? Who is this 4%?
That's easy. These are vaguely worded questions, and different people will interpret them differently. What is the "decision point" at which we're evaluating the morality of one decision vs. another?
If you have someone who disapproves of sex outside marriage and disapproves of abortion, then they might interpret the "approval of an unmarried woman having a baby" as a judgment over whether that woman should have an abortion. They'd say that she shouldn't have had sex in the first place, but once the pregnancy happened, she should have the baby.
So that person might answer "disapprove" of sex outside marriage and "approve" of unmarried woman having a baby.