It has been my experience that in a typical APA 9 ball match, a player completes his total points in 15 innings when playing well and 20 innings when not playing so well. For a skill level 5 (goes to 38 points), when playing well he/she would average 2.533 points per inning or 1.9 points per inning when not playing so well.
Any player averaging 6 points per inning would be skill level 9 (6 X 15= 90 points). A skill level 9 only needs 75 points to win the match.
Points are scored 1 point for each ball 1-8 and 2 points for the 9 ball.
Innings calculations in this post do not account for defensive shots.