Hi Brenda,
There's nothing wrong about the expression 'de bonne heure' for early but it is used slightly differently.
The lesson refers to a specific time and you can be 'en avance', à l'heure , ou 'en retard'. So the train expected at 13 42 will be any of these.
You would use 'de bonne heure' when you mean 'tôt' and the sense of earliness is less precise in my opinion.
Nous sommes partis de bonne heure ce matin pour éviter la circulation. (We left early this morning to avoid the traffic.)
Essaie de rentrer de bonne heure ce soir! (Try to come home early tonight !)
Hope this helps!
