Need clarification on standard pegging in ASCP

Hi , 

Need to understand the standard pegging in ASCP. we have onhand qty for 10 and we have sales order for 10 in week2 and forecast in week 2 for 15(we have consumption and so forecast value is displayed as 5 in week 2). There is a workorder demand from an assembly item for 25 on week 7. planned order demand from week 7 for 5.     we would expect the onhand qty to be pegged to SalesOrder so that it can be satisfied.      we use standard pegging and what demands should we expect to be pegged to onhand qty.      But in