FYI, I don't know the exact rules for "Line Cutting". I assume each shoot is different.
However, when I am asked if a shot is in the 12 ring or the 10 ring, I use the "Rule of Tennis".
In Tennis, you have to see the ball as CLEARLY out. If you have to guess or have the slightest question, the ball is concidered in.
For example: if you are playing Doubles and one guy sees the ball as "in" and the other guy sees it as "out" the ball is "in".
Another example: if one guy says "well, I don't know, looked like it MIGHT be in, then it is "in".
That is how I prefer to score the shots, when I am asked.
Matt