What is the meaning of signs and numbers appearing in scoring system of AAAI?
I dug up my AAAI reviews from two years ago, and it looks like they've been tinkering with their scoring system, so I can't tell you a precise answer.  I can give the general principle, however:
EasyChair allows the chairs of a conference to configure a set of &quot;attributes&quot; for scoring.  Each attribute gets both a numerical value and a descriptor.  Some examples from AAAI two years ago:
Individual attributes:

5: (ground-breaking (top 15%), a sufficient basis for accepting the paper)
4: (positive, a factor in accepting the paper)
2: (problematic, a factor in rejecting the paper)

Overall ratings:

2: (Strong acceptance.  A 5 or 6 in some category, no 1 in any category.)
-2: (Strong rejection.  A 1 in some category, no 5 or 6 in any category.)

So as you can see, then they were using a 1-6 scale and a -2 to 2 scale.
From the sample you gave, my guess is that they're currently using a 1-10 scale, with 5 being neutral.  Thus

8 (+++)

Would translate approximately to &quot;8 out of 10 (a very good score, three positive steps above neutral).&quot;