Rapid Change of Times

I went to Alexander to ask if I could be trained in a particular program.
"Not today. I have an art class."
My sense is that Alexander doesn't need an art class, but okay. We tried to schedule for Tuesday.
"12 o'clock," he said.
"Okay."
Then he paused. "Well, actually, I have something to do. 1:00."
"Okay."
Another pause. "1:30."
I snorted at him. "Well, I'm just trying to be realistic.
Oh, he thought I was annoyed. No, I just though his rapid change of times was funny. "It's fine, really." (What am I going to do about it anyway? Demand?)