Order Level discount is not calculating properly when cascading discount exists on same order.

I am trying to create an order with cascading discount and  order level discount on the same order .For this I created 3 modifiers for cascading discount and 1 modifier for order level discount.

 

    modifier1 --> 10% discount on base price list amount.

    modifier2 -->10% surcharge on price list amount after modifier 1.

    modifier3 -->10 lumpsum on price list amount after modifier 2.

 

    modifier4 -->10% discount on order.

 

  After creation of above setups, I created the sales order with a single line with list price $100. It got adjusted to $79, arrived at this amount as shown below:

 

First Modifier Impact:   100(Actual list price)-10(10% discount)=90

Second Modifier Impact:  90(Derived price)+9(10%Surcharge)=99