This has been confusing me for quite some time now:

When the fake crash is discovered, all the reports seem very sure that all 324 people aboard Oceanic 815 are dead, as though they had sent down a camera and accounted for every single body. It seems possible that they did this, especially since they keep repeating that number. They would have had to explore the wreck pretty thoroughly to retrieve the black box, at any rate.

In that case, where on Earth could the Oceanic 6 have come from? Isn't there a dead body somewhere on that fake plane that's supposed to be Sayid, and Jack, and so on? If 324 people boarded 815, and 324 bodies were found on it after the crash, where did these extra 6 come from?

Or do you think they didn't bother to count the bodies, noticed that most of the seats seemed to be full and concluded that the chance of anyone managing to escape the plane was so remote that there probably weren't any survivors? If that's the case, it seems to me like some pretty shoddy reporting to keep repeating that 324 dead passengers were found.

[...]
In that case, where on Earth could the Oceanic 6 have come from? Isn't there a dead body somewhere on that fake plane that's supposed to be Sayid, and Jack, and so on? If 324 people boarded 815, and 324 bodies were found on it after the crash, where did these extra 6 come from?
[...]


Well, where to get another plane crash in the first place? Since the plane shown on TV was in the midst of the ocean, while the oceanic six claimed to survive nearby an island. (Jack confessed, Kate was pulling bodies out of wreckage and so on.)

My guess: They will conclude that the plane shown on TV isn't 815 at all.

I think they just simply stated that everyone on Flight 815 died in the crash. Whenever there is a crash, they don't go around and just and find every single body. If not survivors are found, then they just state that everyone on board died.

When the O6 are found/discovered they simply find survivors.

But to answer your question, I don't think they count every body, if there are no survivors then they just assume everyone died.