Arico said: In my experience you really don't need to be so hung up about these numbers. You can always change your growing medium to your own liking and fertellize afterwards with liquid feed if need be.
Important for citrus is good drainage, so adding perlite or vermiculite (I'd say 30% of the total volume is good) is a great way.
Stay away from woody growing media though. They're good for epitphytes; not so much for lithophytes.