Consecutive edits only produce one version in the history (see the page's history.) As only one version is stored in the database, only one setting of minor/major edit is associated with it (which is the last one.) It is this way as many people have the habit of saving a page, detecting an error, editing again etc. Actually, whenever you see that there is a gap in the version numbering in a page's history that is what actually happened. Note that this "last edit counts" is not only true for minor edit, but for the summary line as well.