Im not quite sure on what distance to specify for my rear speakers.

I have them both on corner shelves high up above the door (i know not a good place but this is the real world as alot of you no-doubt can sympathize with).

My sette is back against the wall as the room is small.
On my sony reciever i can specify their position but i think this only aplies for sound fields eg Cinema A,B,C modes. I can set position to side, middle or rear and high or low.

Side is as says to the side if i was to be sat a few feet off of the wall. Middle would be in the corners of the room (which they are) and behind is well behind.

So i'm sat at the rear wall with the speakers way up in the corners of the room. That leaves them to the side right? or behind?

Please help me to measure the right distances.
Thanks
John