Is This a One Weapon Attack?

I love these key points. I think this one... Two flurry of lows. Oh, that was almost natural 20. 14 plus eight. That hits. The second one is... 11 plus eight to 19. Both hit. So damage for each of those. Just bludgeoning the hell out of this mutant duck. And you have an additional attack for me? Unbroken air! It's an extra action which you can use for a one weapon attack. But it would not be able to be used for this. Apparently, I don't understand how it works.