IJVM, what means the numbers next to the method names?

Question

I have the IJVM Simulator I got with the download example code. I don't understand what the numbers next to the methods mean.

First example

Second example

I understand that I am calling the add method above, but then what are those 3 and 1 next to add? Why am I including them?

Or the 2 and 0 for fak?