Will my card grade a 10?
In short: I cannot promise any grade, and nobody honestly can. I give you an opinion of the likely range and my reasoning; the grading company decides, and my record shows what I saw and when.
Grading is done by people at the grading company, to their own standard, on the day your card reaches them. I can read the same things they read (centering, surface, corners and edges) and tell you where the card likely sits. I cannot tell you what they will decide.
What I can do is keep myself honest. Every pre-grade that goes through the hub is logged against the grade that comes back, and I will publish that calibration once the record is large enough, rather than claim an accuracy I cannot show. See what I check when cards come back.