Windowskin isn't working

[Soupnazi]

Okay, so I made a windowskin, but then when I put it into the game it made these ugly square thingies at the edges of the boxes, here's a picture:

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And here's the windowskin:

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What is wrong in the windowskin that is causing this?

 

[Glitchfinder]

The top right box in the the image is the problem. The outside of that is the border, and the inside is a series of images that tells people that the window is larger than is actually being shown.

 

[Soupnazi]

Okay, can you explain that in noob terms? I can't understand the "The outside of that is the border, and the inside is a series of images that tells people that the window is larger than is actually being shown" part.
Gosh, I can't understand anything, can I?

 

[Numb]

...
Here:

 

[Soupnazi]

Thanks.
*Feels terrible*

 

[Glitchfinder]

What I was trying to say is that it uses the outer 16 pixels of the top right box of that image are used as a border for the window, and it divides the inner portion into a set of arrows that are only displayed when the window is too small to show everything it is supposed to show.

 

[Soupnazi]

Oh, okay.