This is one of the big failings with numerical grading as it's done. For the upper grades, there's some degree of consistency. While there's differences between one card and another, most 8s will look similar. If they're different it's along the lines of "that's nicely centered, too bad about that one corner" Or "nice corners, too bad it's not centered all that well"
But at lower grades, there's lots more room for differences.
On Quillen I was expecting better than a 3, but missed an erasure on the back. (Like never saw it in over 30 years missed it)
Young was a pleasant surprise, I was expecting a 1, maybe a 2 because of the crease.
even lower grade cards can be much farther apart.