The idea is to decouple Pega managed file from your own automation. If your pega team decides to makes changes, you don't want to own these changes, but you do want the deployments to continue running regardless of who made the change. In this particular case, it's the space requirements for deployment.
Step one is to parse the XML and pull out the space requiremnt (via ruby 'cause we're running deployments via Chef)
Step two is to use that value in some meaningful way.