Alright I will explain these as well and thorough as possible.
Here is how to Increase and Decrease Team Overalls.
Example for Increasing:
Lets say that you want the Colts to go up by some points you will have to increase the Player Ratings then do a transaction, then the Team Overall will decrease.
Example for Decreasing:
Pretty much the same as Increasing but you will have to decrease the player overalls then do a transaction so then the team overall will take a hit.
Example for when you want to Decrease and Increase player:
Overalls but don't want to effect the team Overall.