Mixed PC and Mac licences

I have an iMac, a Windows Netbook and a desktop PC. According to the Avast licences page, all my computers are covered by an Avast licence. However when I try to renew my licence from my Netbook it only shows the Netbook and desktop (Windows) licences. I want to ensure when I renew my licence that all 3 computers are covered rather than just the Windows machine.
Will the single licence cover all iMac and Windows machines?