when i cancel one complex PO,the po line's quantity is error.How to resolve it?

i create one complex po by Buyer Work Center . And i have do some Work confirmation for some Pay item.  The Data is follow. When i cancel the complex ,the line quantiye is change to 140 and the PO line amount is error. How to resolve it ?

PO LINE  QUANTITY	Pay Items number	Pay Items quantity	Quantity for Receive
100
	1	100	80
	2	100	60