Select YTD Average +X% to create a budget that computes the year-to-date average for the actual months in the current year, and uses this average for the forecast.
The simple trend and seasonal forecasts can change depending on how much data is included in history. For example, you may want only recent months included in the trend. Also, if you've loaded data starting in January 2003, you want to exclude months prior to that from being included in the calculations.
Click File / Save As to save different versions of the budget.