The governor just said that number was inaccurate. Here's a link to the coverage of the press conference. https://www.oregonlive.com/politics/2020/09/with-oregonians-... .

Basically the 500,000 people was all the people in any sort of evacuation preparation zone. That includes everyone in a level 1 evacuation zone. That's the be ready level. There have been less than 100,000 people actually evacuated in a level 3 zone according to the press conference. That's still a lot of people, but not as many as had been reported. It's still horrific for everyone that's been displaced.