The Register and Leave button share same Performance Counter called Register Click and Update button uses a one more Counter called Update Click. This example form increments the Counters Register Click and Update Click when user clicks the relevant buttons Register and Update. The Leave button will reduce the Register Click performance count by one. This example looks hollow. But it is just for a tryout purpose.
In the real case, these kinds of click counts are useful to measure Performance of the Operator. Say, for example, a click count on the print button measures how many billing is done in an hour by an operator on the billing counter of a retail shop. The perfmon can plot the graph over time, showing how many billing a billing counter staff clears. You can think of a better example than this one once you know how this Example works.