The cover is one flat PDF sheet containing all three panels. Getting the spine wrong is the classic reason a cover is rejected, so the plugin calculates it for you.
Spine width per page:
- White paper: 0.002252 inch per page
- Cream paper: 0.0025 inch per page
Spine width is the page count multiplied by that per page thickness. Set your paper type once on the Settings tab and pick the same paper when you upload, because cream is slightly thicker and produces a wider spine.
The full cover sheet size:
The cover sheet always carries a 0.125 inch bleed on all four sides, regardless of whether the interior has bleed.
- Sheet width equals two times the trim width, plus the spine width, plus 0.25 inch for the left and right bleed
- Sheet height equals the trim height plus 0.25 inch for the top and bottom bleed
Which page count is used?
The spine math counts the book's content pages plus the two pages the plugin adds automatically, the title page and the copyright page. It never uses a figure below 24, which is the minimum page count the plugin assumes for a paperback.
Spine text:
The title is only drawn on the spine when the book has 79 pages or more and the calculated spine is wide enough to hold readable type. That threshold matches the point at which a printed spine is wide enough for text at all. Shorter books get a plain spine.
What is on each panel:
The front panel is your cover art, cropped to fill the panel and running into the bleed, with the title near the top and the author name near the bottom drawn as real text with a soft shadow behind them for readability. The back panel and spine are filled with a solid color sampled from the average color of your cover art, with the title and a blurb on the back. The blurb comes from your listing kit description if you have generated one, otherwise from your premise, and it is trimmed to keep it inside the panel. Text switches between white and dark automatically based on how light the sampled color is.