A map of the town that Annie and Barbara live in can be represented by the Cartesian plane. Annie is located at $(5,-11)$ and Barbara says she is located at $(-7,13)$. They agree to meet at the midpoint of the segment formed by their current locations. However, it turns out that Barbara read the map wrong, and Barbara is actually at $(-5,5)$. What is the positive difference in the $y$-coordinates of where they agreed to meet and where they should actually meet