the dimension will want to align either parallel to a line drawn between the 2 pick points, or orthographic to the drawing orientation (edges of the paper). you only have one chance to set this, if you get it wrong you have to delete the dim and do it again. the points you selected are very nearly, but not quite vertical, and you've chosen, by accident, to dimension the absolute distance between them instead of the vertical distance. the numbers facing the wrong way are actually help full here because it makes it obvious your not dimensioning the distance you intended.
selecting a line for one of the pick points in stead of a point will force it to align the way you want.
this screen cast should make what I said above a little bit more clear-
https://knowledge.autodesk.com/community/screencast/7d16b3e7-668d-474c-9366-4f7ddce6a817