I don’t think that’s quite correct.

If you look at the first question for example (page 8), it says that 25% thought that Obama won, and 67% thought that Romney won (of the total). But if you look at the figures for whites, it is a little different: 20% thought Obama won and 71% thought that Romney won. So there must have been some non-whites in the sample. Otherwise the two numbers would be exactly the same.

The “N/A” probably just means that the sample size is too small to report (it would have a big margin of error).

If you look at the “favorability” thing, though, it seems that this was a fairly pro-Romney sample to begin with, compared to the national average. In most polls I’ve seen, Obama has a higher favorability than Romney, but in this one it was reversed. And the numbers for both candidates barely budged between before and after the debate.