Proud professor moment
To extrapolate means to draw a conclusion based on information already available to you. That’s pretty much all you need to know to understand this professor’s printed t-shirt. It’s not rocket science, and most people could guess what extrapolate means by looking at the context of the caption.
However, two students in this professor’s class were a bit on the slow side. When two students asked whether the shirt was missing a second part, this had to be the professor’s biggest SMH moment. Those two students who bravely voiced their ignorance are the second type. A safer question would be to ask for the definition of extrapolating.