Because line 6 of the xml file says this:
Code:
<version>1.2.7</version>
You can change it there or in the product manager in vBulletin to say 1.2.8
We hadn't planned on making any more releases for 1.x so we made a hasty release to fix some minor annoyances that some users had.... and forgot to change the version number in the xml file it would seem.
It's probably not worth uploading another version to vbulletin.org to fix the typo since it was just released. If for some reason we make another 1.x release I will make sure it is updated but most of our efforts are in the important code for the upcoming 2.0