Amount of edges

hi all,

having simple code such:

public void listEdges() {
try {
Solid mySolid = (Solid) currentSession.GetCurrentModel();
int edgesQTY = mySolid.ListItems(ModelItemType.ITEM_EDGE).getarraysize();
currentSession.UIShowMessageDialog("EdgesQTY: ," +edgesQTY, null);
} catch (jxthrowable e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

I receive different results. when I have a simple solid part with one extrude feature (10x20x1) as e result I get :12 edges, but when this same is launched in sheetmetal part jlink shows 20 egdes. 

Any idea??