Keep in mind that "not selected" is not just pages. In my case the "not selected" are almost entirely 301 redirects.
Its not useful for me for Google to report things other than actual pages that it has chosen not to index. I'd prefer them to have lines for "pages indexed", "pages not indexed", "errors", "redirects", and maybe "other".
Another bug with this graph that affects me is that subdomains get rolled up. I have example.com (no www) that serves my English content and es.example.com that serves my spanish content. I can't get stats on just my English site because all the language subdomains get rolled up under it in these stats.
In my case, the numbers on the graphs of indexed pages haven't changed in months.