Help CenterSee the image below for some understanding of do's and dont's and how to prevent KDP from rejecting your book due to issues with the cover. Read below, look at the pictures to understand what to do and not to do. At the bottom of this article we have a link to a video you can watch after going over this article.
DO NOT CHANGE your actual cover, Amazon will say to adjust margins or paper size, they say that because they are looking at what you did, and they don't look at the size you selected for the book and or they assume you picked the wrong book size.
#1. Always make sure the settings you picked in the Book Bolt studio are the same on KDP. Trim Size, Bleed or no Bleed and Paper Type.
Left side of cover in Book Bolt (Back Cover).
Right side of cover in Book Bolt (Front Cover).
Don't go partially into the red area like this. Image Opacity has been reduced so you see better the red area.
You should be going just past the outer edge of the red area. Image opacity has been reduced so you see better the red area.
Below is the same as the above image, but with opacity at 100%.
Now that you have a better understanding after going over the above, watch the video below as well to help you understand this if you need more help.