KDP added a blank page to my interior. Why?

This is normal, expected book layout — not a mistake:

• Even page count. A physical book is printed as sheets, so the total must be even. If your content ends on an odd page, a blank is added to round it out.
• Right-hand starts. Chapters and front-matter pages traditionally begin on the right (recto) page, so a blank left page is inserted when needed. See Why did the formatter insert blank pages?

Our Interior Formatter already handles this the professional way, so your PDF arrives correctly paginated. If KDP added one on top, it's just enforcing the even-page rule. It's how every printed book works — flip through any paperback and you'll find the same blanks.