The one thing she repeated in the conversation is ask how the teacher uses map scoring to differentiate his learning with specifics. I think it sounds like a good question, but I'm not sure how to ask it without offending the teacher.
I'm not in a district that uses MAP testing, but I think I understand enough for this question here.
If I were in your position, I would ask the teacher: What were his MAP scores? What does the score means relative to the kindergarten curriculum? Given these data, what's happening in the classroom so that he makes a year's worth of growth this year?
It can be a data-driven conversation, and it puts her in the position of explaining what it means to you. You will be well served if you can get the MAP scores before the meeting and get a sense of where that puts him relative to typical kindergarteners. Ask the questions anyways, and have her walk you through them. When I approach things in this way, I find that I rarely have to get to my third question above because if I sit back and let the teacher keep talking about what the scores mean, they will often come around to "well, of course, I'll be doing x, y, and z to keep Johnny moving forward from this point."
