"More about this stuff":
a) If your first post was as a sticky, it would have a grey background.
b) Your second post was published under UTC -8, but the first was the pre-made "Hello World" post, published under UTC 0: so, according to their current timestamps, the first post is newer. You should check their timestamps in the post editor and change the one of the two to correct the situation. (Or you can forget the timestamps and turn the date of the second post to Feb 28.)
c) You have changed the title of the first post, but its slug (see here: http://en.support.wordpress.com/posts/post-title-url/ ) is still "hello-world". You should edit the post so that the slug reflects the actual post title (post editor: below the title box you can see the "Permalink"; click Edit, change slug, click OK, click Update Post).
d) You would have avoided all that if you had deleted the sample post and created two new posts instead of producing your first one by editing the sample.