Amazon KDP may reject your book from the review status. They may mention to fix your margins and such, as well as specify some or all page numbers there is a prolem with. 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.
You DO NOT acutally change any margins or sizes, 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. you need to fix what is inside the margin area.
If you are reusing an interior for a low content book and just making a different cover, or, just like to make your interior and cover seperate for some reason. You pick Cover only, you must enter the number of pages your interior is. Do not leave it on default of 24 pages or enter a random number you think your interior will end up. If you insist on doing these seperatly, finish the interior first, so you know how many pages it is, then create your cover only and enter the interior number of pages. A 100 page interior will not fit inside a cover made for 24 pages.
#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.
See below example of do's and don'ts.
If you want a large image on your page, that is fine, but you must stay within the dotted green line or fill the page like the next 2 examples show.
In below image, you will see the picture is past the White area of the whole page. This is fine, just as long as it it just past. Opacity is turned down in the below image, so you can see the white area a little better.
See below what is not okay. It is not within the inner green dotted line and it does not fill the page.
Below is an image with text in it. So while the image fills the page and that part is acceptable, words in an image, still can't go past the inner dotted line into the margins. Opactiy is turned down in this so you can see the page as well.
Now that you have read this article and seen pictures of what to do and not do, you can also watch this video below.