A general rule of thumb is to start with the farthest bleeder away from
the master cylinder and work in.  Therefore if there's two bleeders on
the RR you should do the outside one first then the inside.

That said, that's is just a general rule of thumb and a default for
working on any car when you have no better guidance - if Porsche has a
different official recommendation, you should follow that instead.

nate