It's been my impression that the vast majority of scanners which show what's "currently" being scanned (whether an individual file or just the folder it's in) work pretty much the same way, what the display shows is the last one completed. I've often noticed the same as you, that it's showing as "current" what you know is a relatively small file (or folder) for a long time because what it's actually scanning at the moment is the next one which is much larger.
Not a big deal to me, since I try to avoid doing anything else on the computer while I'm running a scan and find something else to do in the meantime, like a hand-held game or catching up on my reading or looking for something to eat.
