Imagine a trial where 20 out of 100 untreated people die whereas 10 out of 100 treated people die. The relative reduction was 50% but the absolute reduction was 10%.
And that's what puzzled me. He said the reduction was 35%, and in his apology he said that he had previously implied that the 35% was an absolute number, rather than a relative number.
I of course did not think it was an absolute number even when I heard it the first time. You can't have an absolute reduction of 35% in deaths when only 1% of the people die. It could only be a relative reduction.
What disturbs me here is that the story goes like this:
Trump says, "Awesome news! Great treatment! Yay, me!" (Or words to that effect.) During the announcement, the FDA head says something that could be taken incorrectly.
The next day, FDA guy says, "This is what I meant. Sorry for saying the other thing yesterday." (Even though, really, it was still fairly obvious what he meant when he said it.)
The press reports: "That stuff Trump talked about yesteday doesnt really work, and scientists are really mad at him and his buddy at FDA!"
Trying to read through the politics, it sounds to me like this is a really good treatment that produces good results. It's not some sort of miracle cure, because most of the people who would have died will die anyway, but a significant fraction will not. Also, there's not a whole lot of available plasma, so it's not like everyone can be treated with this technique. So, no panacea, but still some good news.
That's not what I'm getting from the media headlines.