Hi Jane,
Please follow the step by step process as mention in below :
1. Go to Administration ->System Intialization -> Document setting.
2. Click on Per document Tab.
3. Select sales Order and check box on "Reopen Doc. by Creating Returns/Goods Returns/Credit Memos Based ".
4. Click on General Tab.
5. At bottom , Entered 30 in " Display Canceled and Cancelation Marketing Documents in Reports" feilds.
6.Update
7.Open the Goods Return Document .
8. Right Click And Select the Cancel option then Add the Documents.
9. Then you will find the Goods Receipts Po Documents are Open status.
10. Then You Create the Goods returns with correct value.
I hope this will help you
Rgds,
Kamlesh Naware