promotion modifier problem

I have made a promotion modifier ,the  line modifer level  is LIENPROUP

the promotion is buy item A or B ,if buy two (can be one A and one B or two A or two then get Item C  one 

if i create a order line which item is A, the quantity is  two  and save the line , so it will create a promotion line C by system ,the quantity is one  .I can  find the adjustment line in table oe_Price_Adjustments and the relation information in table Oe_Price_Adj_Assocs

when i create the other line which item is B ,the quantity is  two  in the same order ,  it will change the promotion line C  and the quantity is two .I can also  find the adjustment line in table oe_Price_Adjustments but can not find the relation information in Oe_Price_Adj_Assocs  for the new order line.