http://www.pokecheck.org/?p=detail&uid=4080228
The egg hatched location must exist in the game version of origin for 4th gen format eggs, unless the Egg Received location is Link Trade. Example, in Solaceon Town does not exist in HG/SS.
Edit: Could there be mouseover text for CntSt to explain that it means Contest Stats? Also, come to think of it, that applies for 5th gen eggs, but even when traded (ie. no B/W1 version w/ egg hatched at Virbank, or B/W2 version w/ egg at Route 10). Just not 4th gen eggs in 5th gen format (hatch location becomes Poketransfer).
Oh and of course, Cold Storage and PWT have the same hex for the location.