If you have some progress you can use a progress bar to show this progress.
So, if you copy some files and have already copied about 60%, you may see something like this:
Knowing this, what’s wrong with this image?
Why the heck do I get an indeterminate progress bar for a download progress. Hell, there’s even a percentage displayed for the download.
To me the real mystery around the Windows Update tool has been the progress counter in general. The percentage moves in totally weird steps. Might stay at 0% for a long time, then suddenly jumps to e.g. ~50% and stays there for a while again and so on. Just amazing how it can be like this (and pretty much been since WinXP) considering how integral tool it is for Windows (or was, until W8).
Of course best part is after you restart the computer, you get the “configuring Windows” (or something like) screen, again just with the percent progress bar with no indication whether this is going to take seconds, minutes or hours…