Reading online, I understand the git revert cancels a single commit from the past, but I am unclear as to what that means unless the cancelled commit is the last commit performed.
For example, observe the following three versions of a file:
"a" => "aa" => "a|a"
If I reverted the 2nd version, what would the 4th version look like? "|a" or "a|"?
Revert work by creating a patch which is the opposite of the changes introduced in the commit you want to revert and try to apply it, then create a commit.
If the patch do not apply due to some changes introduced by commits in between, you will have to resolve conflicts...
I hope it will help you better understand how it works.
PS: your notation won't help to understand and explain how revert works because changes are at line level and not file one...