Retriggering of Release Strategy

Hi,
I have release strategy for PO based on characteristics Purchasing group and document type.
under what circumstances will the release strategy be retriggered again.Will it be triggered after the PO is released and then i change the Purchasing group the PO be reset if only the characteristics value change (as i have only the Purchase group and document type as the characteristics)

What happens if the quantity changes or value changes?How can the Release Strategy be retriggered then?

Also can any one please tell me the use of these indicators in the release strategy

1. Cannot be changed (does it mean that if you set this indicator then no matter what changes you do for your PR or PO the release strategy wont be retriggered once the PO is released?)
2. Changeable, no new determination of strategy (what does this config do?)
3. Changeable, new release in case of new strategy (what does this config do?)
4. Changeable, new release in case of new strat. or val. change What happens if we set this indicator)
5. Changeable, new release if new strategy/outputted (what does this config do?)
6. Changeable, new rel. if new strat. or value change/outputted (what does this config do?)
7. Changeable, new release in case ohe new strategy (what does this config do?)

Thanks