Counter, annotation in task definition


Hi everyone

I have just started using and I find it very useful. I wanted to ask you about the ability to add a counter number in the task definition. The goal is to provide such a counter for the user, so he can see how many times this part of process was accessed. I found nice video that shows this approach, but I was not able to fine any API, or example implementation for this. I am talking here about those blue circles in the corner of tasks. Here is lik to video:

Here is screen of this feature:

What kind of feature of bpmn is it ?