PO Release Strategy

Hi MM Gurus,

At my client,PO are going for release procedure based on purch. group,purch org,PO document type and net value.

But characterstics of net value and PO document type are not assigned to the PO Class,still the PO release is triggering based on the above four characterstics.

Is there any other confirugation settings to trigger release?

Please help me.It's urgent as i have to configure a new release strategy but unable to understand the present release procedure.

Thanks and regards

Dinesh