Something wrong with screencapping function

Just got a new Macbook Pro with Retina display, mid-2014 model. I had all the stuff imported from my previous MacBook Pro (2011 model) with Yosemite transferred onto this new computer.

With my old computer, I could do Command +Shift + 4 to screencap any area I wanted, no problem. But now, the screencaps I take are bigger than I expected. For example, I noted that when I took an example screenshot, I took it at 255 (width) by 100 (height) px. When I open it up on Preview, it looks the same size as when I took the screenshot. But when I examine the dimensions in Tools --> Adjust Size... , it turns out to be 510 by 200 px, doubled in size. I first noticed this after I uploaded a screencapped image to a website, where the image was twice as big before.
Said example: http://i.imgur.com/NQHe6H7.png

Is there a way to change this? My internet browser (Google Chrome) was at a standard 100% in terms of zooming in/out when I took the screenshot, and I can't think of how else to research this problem. Downloading images from online has no effect on their size (after I confirm dimensions in Preview and uploading to a site), so I assume it's the screencapping function.

 

I only just found this out through http://www.macissues.com/2014/03/29/adjust-retina-macbook-screenshots-to-be-actual-size/

But luckily, I found a link in the comments showing me a workaround: http://blog.lanceli.com/2012/08/downscale-screenshot-at-hight-resolution-on-retina-mackbook-pro.html

EDIT: I'm still facing some trouble with this method though. Hold on...

 

After following the directions (I did Step 1 and Step 2, without installing that GitHub thing), still doesn't seem to work.

It works perfectly fine when I test my "HalvingScreenshotSizetoNormal" in Automator, in that I get a double-sized screenshot and a normal screenshot saved to my Desktop. But whenever I use Command + Shift + 4, it only does the 1 double-sized screenshot. So I think I'm implementing the function incorrectly; could anyone help me out?

Additionally, I'd appreciate if someone could provided a modified version of that "service" to produce *only* the "normal" screenshot on my Desktop.

2 images of what I did in the Shortcuts pane of System Preferences --> Keyboard: http://imgur.com/gKu3uHM,yQjEnI7#0