Since this is the Pro Version, you get many additional features: a low light setting, a picture gallery, a glossary of terms, a breakdown of the hierarchy of vessels (Rule 18), cheatsheets for sound signals (Rules 24 & 25), direct navigation to specific questions, and quiz settings.
This app is continuously improving thanks to user feedback. However, as I am a mariner myself, there will be significant periods with no updates while I'm underway, but I'll still get your feedback.