My brand new iMac is a late 2015, 2.8 GHz, 21.5 inch purchased from B&H. When I look up the specs by serial number, it shows: Order MK442LL/A Model A1418 (EMC 2889), as it should be. But under the stand, where some info is printed, the EMC is listed as 2833 (which is for the 4K Retina model with the 3.1 GHz processor). Anyone elses show two different EMC's? This normal?