Assets file in Published Rise Output Continually Grows

I built a fairly simple Rise course with seven lessons. Everything is working fine; however, I have noticed that every time I make a small change and re-publish for web output, the number of files in the assets folder in the published output increases each time, even though I am adding no graphics or images. At first the assets folder contained less than 50 assets. Now it contains over 200. Also, I noticed there is unnecessary duplication of files. The same photo or graphic file is repeated multiple times with different file name. I understand that Rise seems to make a separate copy of an image for each instance of use on the site, but there are many more copies in the folder than the number of times the image is actually used.

It's not a problem yet, but the assets folder could begin to become unmanageable if this continues. Is there a way to "reset" the assets folder in published output so that it only contains the necessary files once again?