Differences between auto archiving and normal archiving?

I have a little plugin with some reports and all worked fine. Now I tried to apply auto archiving and in generall this works fine, too. The only problem is that the reports in my plugin wont be archived anymore.

Has anybody experienced similar problems or can anybody explain the differences between auto and normal archiving to me? (or is there some docu that goes beyond the user docu of piwik)

thanks in advance