You can choose how many posts to display on your blog (home, archive and label) pages.
Set Number of Posts
1. In the Layout Configuration page, click on the Edit link at the bottom right-hand corner of the Blog box.
2. The Configure Blog Posts box will open.
3. Under the Main Page Options, set the Number of Posts On Main Page – You can select how many posts you want to show up on each page of your main blog page.
4. Click the Save button to save your new Blog Post settings.
NOTE: If you have set your # of posts per page and it isn't displaying correctly on your blog or Label pages, you are likely experiencing Auto Pagination, something Blogger does to regulate page load times.You may have 1 post on a page and 5 on the next page.
See this article for ways to fix Auto Pagination.