When you are documenting screenshots that already have callouts in them, for example I am documenting screenshots that came from Dr.Explain and they already have callouts in them -- it is HIGHLY useful to use very different-looking callouts in your document containing these screenshots to help the reader to more easily see what you're actually talking about, and not get confused by the other callouts that are already in the screenshots.

 

Once again, this is another place that Dr.Explain shines.  Not only is this relatively well documented in Dr.Explain's Help file, but doing a little experimenting with it (e.g. making your own custom Screenshot Annotating Template) allows you to see the effects of every change.

 

These are controlled from the Project settings > Screenshot annotating settings. Once you are in this screen, you have an incredible amount of control on how your callouts appear:  text font, size and color (for the number as well as the label), size, shapes and color of the bullets, line styles, thicknesses, borders, fill styles... and to be fair, I'm only scratching the surface here.  The Dr.Explain team did a really, REALLY good job on this!

 

Finally, if you want to revert to Dr.Explain's default settings, doing so is literally 3 clicks away:  click the "Default" template, OK, OK.