Forecast Explodes into what?

 Hi,  We are exploding ATO Models through Copy/Merge Forecast.  I am seeing inconsistencies in what it explodes to.  Can someone tell me the logic behind this explosion?  What is it "supposed" to explode into?  Here is a sample BOM structure - note we have configurable options:

1) ATO Model

2) Mandatory Component

2) Option Class ( we have several within a BOM)

3) ATO Model

4) Mandatory Component

3) ATO Model

4) Mandatory Component