Well. X-pos of the arrow looks to be just ok to me. Y-size is somewhat out, and I have to say that reading the equations ain't the easiest.
Problem is that your RealImage -sprite has some extra transparent pixels at the top of the image. Image size is higher than the visible area, thus the scaling fails.
Use "crop transparent edges" at the image editor. That seems to image length.
Also.. You can just delete subevents 11 and 12 .. those are not needed at all. Actually it works better without them.