PRange is the player's range, figured as putouts plus assists, divided by games. LRange is the average league range at that position for the player's career. So far, no position player in the LoL got his start after 1997, so I just used the last known league range for active players. RIndex is shorthand for Range Index, which is PRange divided by LRange. This allows me to compare the players to each other directly, without worrying about the effects of era.
Assists is the number of times the player threw out a baserunner.
It's only listed here for outfielders and catchers, as no other position requires an Arm rating. Games is the number of games a player spent at that position over his career. I use it to help figure out arm strength, so again, it's only listed for outfielders and catchers. G is assists per 162 games. This gives me some idea of how many assists a player got in an average year.