900 was a random number used in another post.
“This means that a page with PR2 has 6 times as much power as a page with PR1”
PR is displayed in integers, but pages do not have PR in integers. A PR2.1032243 and a PR2.975243 and a PR3.83625 are related in very different ways, like a 5.1 and 5.9 and 6.8 earthquake.
There is no definitive agreement on the PR logscale, but no way is it less than 6. I’d say it is closer to ten than to six.