I created a blog of one page on Blogger back in July 2008. I don’t have any traffic. My page is indexed in Google, but what does Google "PageRank not available" mean? How can I get Google to say PageRank of "0/10" at least to start instead of "PageRank not availabe?"

Page Rank not available means that the website or webpage you are viewing has not been rated by google yet.
I don’t think you’d be able to change the notification message to 0/10. Because, if it is shown 0/10, it means that the page has been analysed and ranked the least.
And hence the notification of unranked pages is "PageRank not available".