In 1977 he was interviewed by John M. Steiner and Günter Bierbrauer. The following extract from the interview is about the Auschwitz death toll. Erber, who dealt with the transports and was definitely in the position to make an educated guess, estimates that 500 to 750.000 people were gassed in Auschwitz at a time when most people believed at least 2 Million were killed in Auschwitz and when his guess would have been regarded as downplaying and minimising. Compared to modern studies such as Piper's with including corrections for Hungarian Jews it is remarkable accurate though.
Erber: I estimate that the number of gassed people is between 500.000 to 750.000, but I cannot be certain because I don't have the files anymore.
Bierbrauer: You've said more wasn't possible. What does that mean? More as a Million or...
Erber: We shouldn't forget it was war. Firstly, the transport capacities were lacking and secondly the extermination itself, that didn't work either. I've read in this thing, 20.000 deads per day. Without doubt impossible.
Bierbrauer: Why was it impossible?
Erber: Because it couldn't be carried out. It couldn't have been done.
Steiner: You mean technically?
Erber: Yes. [he says "nee" which means no, but depending on his accentuation he could have meant "ne", which has the sense of yes, which is more likely in this context]
Steiner: So you say about 750.000.
Erber: Up to 750, but that's the absolute maximum.
Steiner: But you don't include people who were shot...
Steiner: ...or died otherwise?
Erber: [incomprehensible]....with the executions at the black wall, these were death sentences mostly, at the black wall and so on and then with the injections and so on, how they spoke about, I calculate 280.000
Steiner: So in total how many people perished in Auschwitz?
Erber: In Auschwitz almost a Million, but this is an estimate.
Bierbrauer: But Mr. Erber doesn't it make a big difference if it were 1 Million according to you estimation or say 2 Million according to others?
Erber: It couldn't be, see I was there from 40 to 45 and so many were not sent there.
Steiner: And you should know it as you were there.
Erber: See, If I knew, I would give the exact number, I don't gain anything from it.
Steiner: And you don't have anything to loose.
Erber: It doesn't help me either.