A map of the town that Annie and Barbara live in can be represented by the Cartesian plane. Annie is located at $(3,5)$ and Barbara says she is located at $(-6,2)$. They agree to meet the midpoint of their current locations. However, it turns out that Barbara read the map wrong, and she is actually at $(-10,4)$. What is the positive difference in the X-coordinates of where they agreed to meet and where they should actually meet?