Did he put the entire 200g on this one acre lawn? Rule 1: NEVER assume anyone knows what they are doing. I tend to learn things as I go and assume everyone else can learn things accurately on the fly too... that belief has kicked my hiny so many times. I will never let my guys mix anything on their own. Its not too hard to get a tech to perform properly in the field but IMO keeping the brainwork to a minimum is crucial (ie: dont ask them to mix).