What you're seeing is not normal. As you can see in the bottom right corner, the scroll bars overlap. That is not supposed to happen. This is what it's supposed to look like:
As you can see, the vertical scroll bar ends at the top edge of the horizontal scroll bar and the horizontal scroll bar ends at the left edge of the vertical scroll bar.
Do you see this behavior if you reboot in safe mode? What about if you log in to your machine as a different user?
I rebooted in Safe Mode and it did exactly the same thing.
FYI, this is a clean install only a couple weeks old on a brand new computer and it's been doing this since first installation.
Also of note is that I posted on a social media account of mine about this and immediately had several responses from friends that this also drives them nuts... so while it may not be supposed to be normal, it's at least one version of normal for this OS....
I tried to duplicate what you are seeing, and connot. My display has the scroll bars correct. Try something as an experiment:
Go into System Settings -- General and check the setting for "Show scroll bars:". I think the default setting for Mountain Lion is "Automatically based on mouse or trackpad". Select "Always" and let us know what the results are.