Difference of 3dB in levels between Edit View and Mix View

Load something into edit and then mix view, look at the Main Meter the 114dB range meter

you will see a difference of 3dB in levels. to check my claim create a Sine Wave in the Mix View Window

 at 440 hertz at -6dB it will load into an empty track, play back the file and check the meter, it will read at -9dB if you now double click on that file and send to the edit window and play it back it will indicate the correct level at -6db. and visually be at -6dB. Now mix down the file you have created in the multitrack Window, when checked it will be at -9dB. "Is this a fault or have Adobe created 3dB OF HEAD ROOM" I would have thought that both Edit and the Multtrack Window should be calibrated at the same level, could someone please pass this on to the right person please.  Roger Mallison Australia