Hi,
1)Goto->CJ32->Open Project->Select WBS
2)Check the available budget means (Released-Assigned), that amount can be De-release.
3) Make sure that your De-releasing amount<=Released-Assigned Budget.
4) Reduce the amount (De-releasable amount) from release budget. Enter new reduced value on Released Budget field against concern WBS.
5)Select the whole Release Budget column->edit->total up->Save.
Regards
Shishir