Licensed Grows Lab Tests - Low Microbe Count? What is that?

I am looking at a commercial license. My friend has a comml license and the lab says they always do well because they have a low microbe count. I sort of said, that is awesome.

I am not sure what it means and what they test for. I assume part of it is low or no powder mildew. What about bugs or wrong pesticides? Anyone know what all the microbes they are testing for? Sorry if this is a dumb question.