The sensitivity test indicates which antibiotics your specific infection is sensitive to. I just learned in a conference this afternoon that the genetic variations number over a thousand, so some strains of the same bacteria can be susceptible to an antibiotic, whereas it's close cousin may be resistant.
Colony counts must be done during the culture process. Some labs simply label none, few, many ... others use more quantitative measures.

Please be assured that watching and waiting, especially if you have few or no symptoms, is a common practice with MAC/NTM, especially if you have had only one positive culture.

So, you have a week to read, here and elsewhere, about this infection and formulate questions for your doc.
I will be interested in hearing what the result of you visit is.
Sue