Now, your book is all complete, but you see that it has some of the defects mentioned above. It has big tears, or stains, or water damage, or the spine is splitting, or possibly all of the above. How do you grade it?
A comic that has all of those defects and looks like the book pictured would receive a 1.0 to 1.5 grade from CGC or CBCS, even if it is complete.
If you have only one of those problems mentioned, then the severity of the defect would be what affects the grade most. If there is only a spine split to your comic, then the grade will depend on how big the split is. If you are missing a small piece, then it depends on how big the piece is.
The best way to understand how a defect affects the grade is to look at examples online. The variety of grades you can receive is hugely dependent on the sum of the defects.