Today I realized there were some changes in Statistics-Crawl Stats section of Google Webmasters area. One of my new websites which got PR3 in the last update and was showing all greens in "PageRank not yet assigned" is now showing some green bars there and a little part of it is in Medium, for the homepage I think. But I have another website which is also PR3 and it has no bar in Medium, it just has in Low. So what is the PR interval of medium in Google Webmasters area? Does it have accurate borders?