Gradin Abbreviations used throughout GPA's pricing data
With respects to the notations next to the grades, as per CGC's old label designation for restored/qualified books:
S = Slight
M = Moderate
E = Extensive
A = Amateur
P = Professional
So a combination of SA, would mean Slight Amateur restoration. When A is used on its own it denotes "Apparent" restoration, which simply means a restored label with a specific qualification
Q denotes "Qualified" grade (a green label).
In 2014 CGC introduced a new way of describing restored books:
Additionally, there is now a "C" for "Conserved" books.
You can read further details on the above new restoration grading scale on CGC's website: https://www.cgccomics.com/news/article/4084/