it only goes up if you get 4.5 or 5 star players. it will not drop the top players and take them out of the draft pool when you are drafting.. so don't trade your players for another pick. unless you want to draft a player you dropped.
So i figured out how this works I think.. if you don't trade your players it will keep all the 4.5 star and above players and you will not re draft them. Its better not to trade in your players if you want to get all the 5 star players.