After allocation run the cost is charged target project still indirect project cost not reduced

I have booked some of expenditure against one indirect Project and defined allocation rule and indirect project is source and 2 contract projects are target projects. i have run PRC Generate Allocation Transaction, it is success fully completed. then i release allocation. Then i run Distribution mis cost and Generate cost accounting events the Allocation amount is transfer to Target projects but still  the cost is not reduced from Indirect Project if i run again generate allocation again the cost is transfer to Target Projects. may i know why it is happening like this Please let me know if any