If you closely look into this blog’s custom modifications, you can find that the blog’s homepage has very less amount of latest posts, the category pages have different number of posts and search results show something else. By default wordpress limits you to show the same number of posts you set up in Options > Reading menu for homepage + single posts page + search results page + category template pages.
Whats the need of Different Posts Per Page?
Generally you would like to show more number of posts on your category pages and show limited number of posts on the homepage because a very long homepage would make the blog look boring. Another reason for Chronological Order is that you would like to show the first posts in your categories because your posts style would be teaching something day by day basis and showing the posts from oldest to latest would be the best solution for this.
Just download, upload & activate the plugin and go to settings menu and change the options in order to show the desired number of posts per page on your wordpress based blog. A Excellent plugin for people who love to play around their blogs and are looking for better usability for their viewers by showing whats required for the visitors.