replace color glitch?

[Darkware]

I made a simple gradient from black to white, then went to Select>ColorRange and used the sample color I had - #848484. I set the fuzziness to 0 to restrict the selection to only that color and then pressed OK. It selected three pixels. I copy and paste these into a new document to make it easier to see them. Now here's the glitchiness: I eyedrop each of the three pixels to see what their hexadecimal values are. One is 848484, another is 848484, but the last one is 848585. Why is Photoshop selecting an 848585 colored pixel when I'm telling it to only select a 848484 colored pixels? I would assume that setting fuzziness all the way down to 0 would restrict the selection to EXACTLY the color you specify, but it doesn't appear to be doing that. Is there any way around this? This is important because I'm trying to select specific colors that are not used as much and replace them with colors used more often in the image.