std cost estimate- setup cost

Hi, we run the std cost estimate for the fert material. setup cost is maintained for the first part only thru sap005 formula in costing view of the wok center. when we create co01 for the same material and calculate the wip, after final confirmation, in variance it is showing as the amount equal to the setup cost as std cost estimate is multiplying the cost with the qty of the prod order. this is showing for the order whose order qty is more than 1. pls advise how can we eliminate this variance as setup cost is maintained for only 1 part.