Seasonal Planning

I got couple of questions to clarify. We are in SCM5.0

1. Forecast Model Seasonal Lenear Regression(35 ), even though we set up the seasonal periods as 12, some times its defaulting to 1.

2. What is the significance of Seasonal Planning check box in Planning Area Info node.

3. Why do I see in display mode of ‘Settings for Seasonal Planning’ in Go to Section.

Your help is appreciated.

thx

Jeff