The screen resolution difference with a retina display
MacBookPro has an effective resolution that depends on the Scale you setup for the display. 



You need to use the effective resolution in your code. You can get it from this code, but it works only when there are no external montitors.

tell application "Finder"
    set screen_resolution to bounds of window of desktop
end tell


Reference


https://stackoverflow.com/questions/11488126/get-bounds-of-desktop-with-applescript
http://osxdaily.com/2014/04/14/change-retina-macbook-screen-resolution-more-space/
http://www.anandtech.com/show/5996/how-the-retina-display-macbook-pro-handles-scaling