These settings offer a way in which to control the offensive players that are in the game for each offensive formation. Each formation has its own depth chart and they can all be different. Additionally, each depth slot has an effective and a distribution setting.
The effective setting is used to set when the player should be taken out of the game and a backup inserted into the lineup because of fatigue. The setting tries to quantify the player's effectiveness in the game relative to when he is completely rested and healthy. For example, setting a player's effectiveness to 60% (the default setting) means that he will be subbed out of the game when he is playing at 60% of his overall effectiveness.
The distribution setting is used to set how often a running back or quarterback should get carries in the running game and wide receivers and tight ends should be the first option on passing plays. The distribution must be set to a number within the range 0 - 100 for the player. The distribution is relative to the other players currently in the game. For example, on the I-Formation depth chart setting QB1's distribution to 10, RB1's to 60, RB2's to 30, and RB3's to 10 means that when a running play is called and QB1, RB1, and RB2 are in the game for the play, QB1 will carry the ball 10% of the time, RB1 60% of the time, and RB2 30% of the time. Using the same settings, if QB1, RB1, and RB3 are in the game for the play, QB1 will carry the ball 12.5% of the time, RB1 75% of the time, and RB3 12.5% of the time. The distribution is slightly different for passing plays -- it does not necessarily determine who the ball is thrown to by the quartberack. It sets who the quarterback will look to first (first progression in his reads), but he may have to move on to another receiver if he is covered or he has pressure from the defense.