avast@ advantage77.com is correct in that Avast cannot read the archives that are password protected.
What did you select for the "Action" to take when you ran the scan? If you have come up clean with all your other scans (Quick, Full, Boot), then I would put "No Action."
You can also run an on-demand scanner if you are really concerned, although I don't think this will catch any archives that are password protected, like Malwarebytes-Antimalware (MBAM), but it's a good back up tool to have that works differently than your normal AV. This also comes as a resident (running all the time) version as well, and is compatible with Avast for a one-lifetime fee.