What to check
1. KDP requires 0
KDP requires 0.125 inches of bleed on the top, bottom, and outside edges of a paperback cover.
2. Spine width depends on page count and paper: white and standard-color paper use 0
Spine width depends on page count and paper: white and standard-color paper use 0.002252 inches per page; cream paper uses 0.0025; premium color uses 0.002347.
3. KDP allows spine text only above 79 pages and asks for 0
KDP allows spine text only above 79 pages and asks for 0.0625 inches of clear space on each side of the spine text.
Use the final production inputs
Calculate from the final formatted page count, not the manuscript estimate. Select the exact trim, binding, interior type, and paper stock before creating the cover sheet. If any of those values change, regenerate the dimensions and compare the exported PDF against the printer's current template.
Artwork, type, spine, and back-cover copy remain editable when the print setup changes.
Sources: Amazon KDP cover preparation. Recheck the current printer template before export.