Steps to Reproduce:

       1. Place a comparator leading to redstone.

       2. Place a chiseled bookshelf next to the comarator.

       3. Place/take books in/from the bookshelf.

Observed Results:

The first book placed/removed is not detected.

example: comparator shows 3.

Add 1 book in the bookshelf, comparator still shows 3.

Add another book, comparator now shows 4.

Remove a book, comparator still shows 4.

Remove another book, comparator shows 3.

Expected Results:
The comparator should show the exact amount of books.

example: comparator shows 3.

Add 1 book in the bookshelf, comparator should show 4.

Add another book, comparator should show 5.

Screenshots/Videos attached: https://we.tl/t-qC1r5NmdxU