The Ottoneu arbitration process starts 10/15 and takes 30 days, but you can actually use the Roster Organizer to budget for the impact of arbitration well in advance.
Select an open roster spot on your organizer and “click to add target”. Then just type in a name in the field (“arbitration”) and add a dollar amount for the arbitration you expect to receive (I usually just assume the full amount of $33). Then adjust your roster organizer by player/position as the overall roster salary will reflect the cost of your players and the arbitration you are set to receive on 11/15.
More about the Roster Organizer