This explanation actually provides 2 examples, one before the description text and one after. The description refers to the example before:

> listenTo object.listenTo(other, event, callback)

I think changing the naming to be more specific and updating the description names could help out.

   listenTo  observingObject.listenTo(actingObject, event, callback)

One caveat is that this breaks consistency with the other examples in this section (i.e. object.once(...) object.trigger(...)).