Hi,
As per the standard process, when PR is created Committment value will be in PR , And with referance to PR when the PO has been created ,the proportionate committment value will be transfered to PO.
Similarly the process will be same with the actuals, the proportionate value of PO commitment will be converted to actauls by GR , Confirmations, and any other actual financial postings.
I hope this might be helpful....
Regards
vrkumar