I had to look this up as well, I was thoroughly confused since I purchased it directly from EVGA so I figured the odds of EVGA selling a fake GPU were pretty low.  I tried searching the HWBOT forums for help but no dice.  From googling a bit I found that GPU-Z can do this for certain NVIDIA cards, and its basically letting me know it may have been tampered with. Given it performs like the GT218, and that there are a bunch of different versions of the 8400 GS, and its running the GT218 vbios and drivers, and since I bought it directly from EVGA and not a third party or ebay seller, I figure it must be a false positive (from the googles it seems false positives were also common).  First I've seen it myself though.