What are the expected behaviors of properties 'PageAutoSize' and 'PageSize' in IFS Print agent?

In the ifs-printing.properties file in IFS Print Agent two properties available as below.

• PageSize               Eg: PaperSize=Portait A4,827,1169

• PageAutoSize      Eg: PageAutoSize=yes

In Apps10 Core environment noticed that either one property is used at a time. But a customer has both properties used at the same time. I could not find a better explanation on the usage of “PageAutoSize” in F1 docs. May I know what is the ideal way to use these properties? Also what is the expected behavior when both properties are on?