Low Plate Appearance Factor: If a player or pitcher has less than 10 plate appearances versus either left-handed or right-handed pitching, his actual performance will not be followed in the game. He will be assigned performance criteria which is below average major league offensive production for his position.

Platoon Factor: Players (batters) who are rated Platoon L (Stats/Rosters-ratings page) are limited to their actual plate appearances versus LHP. After those actual plate appearances, they will become very poor hitters versus LHP. This is to avoid the phenomenon of a left-handed batter who batted over 300 times versus RHP and only 10-15 versus LHP and got lucky for that very small sample of plate appearances.
The same thing applies to Platoon R for their plate appearances versus RHP.