Late to the party, but as someone who uses the 100-point scale hopefully I can be of some help. The way I use it is as a conversion from letter grades, which is the scale that I used previously. There are 13 letter grades, and since I just employed the two outermost grades to denote “flawless” and “irredeemable” (A+ and F, respectively), they only needed one point each (100 and 0, respectively), leaving the remaining 99 points to be divided evenly among the 11 remaining letter grades.
So, each letter grade gets its own range of nine points (excepting A+ and F), and they mean the following:
A+: Flawless (100)
A: Masterpiece (91-99)
A−: Highly recommended (82-90)
B+: Must see (73-81)
B: Solidly recommended (64-72)
B−: Reservedly recommended (55-63)
C+: Take it or leave it (46-54)
C: Pass (37-45)
C−: Avoid (28-36)
D+: Must avoid (19-27)
D: Disaster (10-18)
D−: Atrocity (1-9)
F: Irredeemable (0)
Within each range, it’s pretty much intuitive. When you use the scale for long enough, you know what a middling B is, what a weak C+ is, what a strong A− is, etc. An easy way to think about it when you first start using the scale is to, after assigning a letter grade, ask yourself how “close” the movie is to being bumped up or down a grade. E.g., let’s use the 62 vs. 63 distinction someone mentioned in this discussion earlier. If I’m between those two ratings, I’ve given the movie a B− (i.e., decent but flawed), but in my mind I know it’s really almost a B. So, I would ask myself: Is this movie “pretty close” to being a B (62) or “very close” to being a B (63)?
My advice is to just let it be a gut thing and not to agonize over it. Try to assign a rating shortly after watching the movie so that you don’t go mad trying to recall what precisely you thought of it a week later. Most of all, keep in mind that this scale really only works as an indicator of your own enthusiasm; trying to factor in “objective merits” (whatever constitutes those) will always be a somewhat disingenuous endeavor. Think of it as advising your former self on whether to see the movie you just watched. How much will you, personally, get out of it? The /100 numerical is just a shorthand for your own admiration and/or enjoyment. Hope that helps.