Swiped from the APBA Between the Lines forum.

Position Players:

J-4 is up to & including 61 games.
J-3 is 62 - 111 games.
J-2 is 112 - 139 games.
J-1 is 140 - 156 games.
J-0 is 157 - 162 games.

Starting Pitchers:

J-4 is up to and including 22 games started.
J-3 is 23 - 31 starts.
J-2 is 32 - 36 starts.
J-1 is 37 - 39 starts.
J-0 is 40 or more starts.

Relief Pitchers:

J-4 is up to 31 appearances
J-3 is 32 - 49 apps.
J-2 is 50 - 62 apps.
J-1 is 63 - 69 apps.
J-0 is 70 or more apps.