Even though you have selected to show at-most a fixed number of posts to be displayed in the blogger home page, if your blog has a label link. When clicked on these labels the result page shows all the posts tagged in for that label category. To limit the results and to set the maximum number of posts to be shown in the result page of Labels, you have to just add some code to the URLs of the label.
Just add ?max-results=6 at the end of the label URL. You can set this to any number as per your requirement. In this code only last 6 posts results will be shown in the list for that particular label category.