Well, the color rating from the malsters is for the actual malt itself (an oversimplification to keep it short), not what the color will be when the grain is used in a beer. Most of the *real* high numbers come from the "black malts".
As an example, in the ProMash database look at "Black Malt" from Belgium. It has an SRM rating of 600.
Now, create a new recipe in ProMash. Make it for 5 gallons. Next add "Black Malt" as the only malt, and make it 1 lbs. Note the SRM Color obtained is 39.8 SRM (not 600 which the malt is rated at). Now up it to 3 lbs and note the color is now rated at 84.6 SRM. Now if I took it down to 0.25 lbs (about the amount I might add if I was looking to add some color to a beer) and the contributed SRM is 15.4.
So it's keen to note the color rating from the malster does not equate back to the actual color of the beer you brew. Most of the real dark malts are used only as specialty malts for either flavor or color, in very small amounts.
I would use the actual rating from the malster, regardless of how ridiculous the number might sound.
Hope that helps!