You can turn off Duplicate padding if you don't need it. It copies edge pixels into the padding.
The padding is outside the regions and isn't normally drawn. However, when a game toolkit samples from the atlas page image, it may sample surrounding pixels, depending on your runtime settings. This often occurs when you are drawing the region scaled. Sometimes you want that sampling to be blank pixels, sometimes you want it to be the same color as the region's edge pixels.
For example, if you are drawing regions next to others, like for a tiled background, then you want the padding the same color else you may see seams (1px wide artifacts), especially when scaling.
If you need duplicate padding for some images in your atlas but not others, you can enable Duplicate padding and for images where you don't want it, make sure they have 1px of blank pixels at the edge.
