You can download a single post or backup the whole blog. If you backup a blog, you can choose to go with a full backup, an update, and a check. Update will start processing the latest post and stops when the post to be downloaded already exists. Either a full or an update backup is interrupted, or you accidentally deleted a post, run check mode: it skips the existing posts but doesn't stop at the first instance. Just think: if you started a full backup, then you interrupt it, and if you would attempt to resume it by running it in update mode it would stop immediately as each mode starts from the latest post, and if that post, or an other early one already exists then it will stop there and leave behind the old.