This is quite funny and interesting. I felt this recently when i was making an article. I typed an article what i planned. After completing it , i reviewed it. Found some spelling and grammatic mistakes.I corrected all those. While am in the processing, i deleted a line unfortunately. I did not worry as CTRL + Z is always there to help. But this time CTRL + Z worked a bit extra. When i used the re-do option. The deleted line was restored, in addition to that,the correction what i made before were also rolled back.
This might be a misfunction in Blogger stack. The history gathers more than one item, so that all operations that were carried out will be undone.Weird!!!Adding to it, this is the second weird feature i found in blogger.