"Creasing" question 0

[Danger Haggis]

I recently received 3 Sig Series books that I had signed at a Comic Con in November.  I had all 3 of the books pressed when I submitted.

One of the books came out beautifully - there was a spine roll that got pressed out and the book graded as a 9.8.

However, another book that I didn't think really even needed pressing came back as an 8.5 with this note:

Grader Notes:
creasing to cover

I looked all over the book and didn't see ANY creasing.  Does anyone here have any insight as to what could cause this?

This isn't a high-value book or anything.  I mistakenly thought it was the first appearance of Spider-Punk while I was at the convention (choke pick), but I am curious why it was dinged for having creasing when I can't see any.

[Axe Elf]

If we could see every defect ourselves, we wouldn't need the professionals to see them for us.  If the professionals say it's creased, it's creased.

[The Lions Den]

Light creasing can often be difficult to see, especially through the CGC holder...