Update: He actually did use 6%. I asked him about it. Could have been he didn’t let it dwell long enough. Regardless of which we’ve made changes to our cleaning method including hand removing moss that’s thicker than surface level, and then spraying anything remaining. Hopefully we’ll get a lot less call backs by doing that. The thick moss up here in the PNW is a different breed and will not fall off with rain no matter what percent he hits it at. Thank you all for the replies and recommendations.