Hello AndriDem
I'm fairly new to PR, but from my study and understanding of the system, your initial focus or "statement of purpose" doesn't necessarily need to be overly specific.
Maybe start with something like "I am going to PR this book so I can have a better understanding of the JAVA programming language." Or something to that effect. Apparently the "so I can" bit is fairly important and from memory it is emphasised in the PR course. If I recall correctly it helps create purpose.
Once you have PR, SRead, Dipped (or Skittered?) and possibly broadly Mind Mapped one or preferably several books on the subject you can then narrow in on a more specific purpose for that subject.
I might be wrong, but that's how I would approach it. Good luck.
